Номер 260, страница 77 - гдз по геометрии 10-11 класс учебник Атанасян, Бутузов

Геометрия, 10-11 класс Учебник, авторы: Атанасян Левон Сергеевич, Бутузов Валентин Фёдорович, Кадомцев Сергей Борисович, Позняк Эдуард Генрихович, Киселёва Людмила Сергеевна, издательство Просвещение, Москва, 2019, коричневого цвета

Авторы: Атанасян Л. С., Бутузов В. Ф., Кадомцев С. Б., Позняк Э. Г., Киселёва Л. С.

Тип: Учебник

Издательство: Просвещение

Год издания: 2019 - 2026

Уровень обучения: базовый и углублённый

Цвет обложки: коричневый с ромбами

ISBN: 978-5-09-103606-0 (2023)

Допущено Министерством просвещения Российской Федерации

Математика: алгебра и начала математического анализа, геометрия

Глава 3. Многогранники. Параграф 2. Пирамида - номер 260, страница 77.

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          #hidden: []
          #visible: []
          #fillable: []
          #guarded: array:1 [
            0 => "*"
          ]
        }
        1 => App\Models\Branch {#1118
          #connection: "mysql"
          #table: "branches"
          #primaryKey: "id"
          #keyType: "int"
          +incrementing: true
          #with: []
          #withCount: []
          +preventsLazyLoading: false
          #perPage: 15
          +exists: true
          +wasRecentlyCreated: false
          #escapeWhenCastingToString: false
          #attributes: array:24 [
            "id" => 744382
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Пирамида"
            "field_branch_order" => "2"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1119
              #items: array:1 [
                0 => App\Models\Term {#1120
                  #connection: "mysql"
                  #table: "terms"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:7 [ …7]
                  #original: array:7 [ …7]
                  #changes: []
                  #casts: []
                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [ …1]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "field_page_start" => "72"
            "field_branch_display" => "0"
            "field_branch_expanded" => "0"
            "field_display_branch_in_title" => "1"
            "field_display_task_interval" => "0"
            "field_display_branch_page" => "1"
            "field_branch_title_in_content" => "0"
            "field_navigation_title" => null
            "field_metatags_title" => null
            "field_metatags_description" => null
            "field_h1" => null
            "field_description_top" => null
            "field_description_bottom" => null
            "field_branch_cover" => []
            "field_branch_covers" => []
            "book" => Illuminate\Database\Eloquent\Collection {#1121
              #items: array:1 [
                0 => App\Models\Book {#1122
                  #connection: "mysql"
                  #table: "books"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:50 [ …50]
                  #original: array:50 [ …50]
                  #changes: []
                  #casts: []
                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [ …1]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1157
              #items: array:1 [
                0 => App\Models\Branch {#1158
                  #connection: "mysql"
                  #table: "branches"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: true
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:24 [ …24]
                  #original: array:24 [ …24]
                  #changes: []
                  #casts: []
                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [ …1]
                }
              ]
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 744382
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Пирамида"
            "field_branch_order" => "2"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1119}
            "field_page_start" => "72"
            "field_branch_display" => "0"
            "field_branch_expanded" => "0"
            "field_display_branch_in_title" => "1"
            "field_display_task_interval" => "0"
            "field_display_branch_page" => "1"
            "field_branch_title_in_content" => "0"
            "field_navigation_title" => null
            "field_metatags_title" => null
            "field_metatags_description" => null
            "field_h1" => null
            "field_description_top" => null
            "field_description_bottom" => null
            "field_branch_cover" => []
            "field_branch_covers" => []
            "book" => Illuminate\Database\Eloquent\Collection {#1121}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1157}
          ]
          #changes: []
          #casts: []
          #classCastCache: []
          #attributeCastCache: []
          #dateFormat: null
          #appends: []
          #dispatchesEvents: []
          #observables: []
          #relations: []
          #touches: []
          +timestamps: true
          +usesUniqueIds: false
          #hidden: []
          #visible: []
          #fillable: []
          #guarded: array:1 [
            0 => "*"
          ]
        }
      ]
      #escapeWhenCastingToString: false
    }
    "content" => Illuminate\Database\Eloquent\Collection {#1164
      #items: array:6 [
        0 => App\Models\Element {#1178
          #connection: "mysql"
          #table: "elements"
          #primaryKey: "id"
          #keyType: "int"
          +incrementing: true
          #with: []
          #withCount: []
          +preventsLazyLoading: false
          #perPage: 15
          +exists: true
          +wasRecentlyCreated: false
          #escapeWhenCastingToString: false
          #attributes: array:7 [
            "id" => 938909
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1187
              #items: array:1 [
                0 => App\Models\Edition {#1179
                  #connection: "mysql"
                  #table: "editions"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:21 [ …21]
                  #original: array:21 [ …21]
                  #changes: []
                  #casts: []
                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [ …1]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "task" => array:2 [
              "refs" => "744675"
              "type" => "task"
            ]
            "text" => "<p> <b>260.</b> В правильной треугольной пирамиде DABC через боковое ребро DC и высоту DO пирамиды проведена плоскость α. Докажите, что: а) ребро AB перпендикулярно к плоскости α; б) перпендикуляр, проведённый из вершины С к апофеме грани ADB, является перпендикуляром к плоскости ADB. </p>"
            "img" => array:1 [
              0 => array:5 [
                "name" => "260-1.jpg"
                "alt" => null
                "width" => "1545"
                "height" => 295
                "path" => "/media/geometrija_10/atanasjan-u23/0-00/260-1.webp?ts=1739436493"
              ]
            ]
          ]
          #original: array:7 [
            "id" => 938909
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1187}
            "task" => array:2 [
              "refs" => "744675"
              "type" => "task"
            ]
            "text" => "<p> <b>260.</b> В правильной треугольной пирамиде DABC через боковое ребро DC и высоту DO пирамиды проведена плоскость α. Докажите, что: а) ребро AB перпендикулярно к плоскости α; б) перпендикуляр, проведённый из вершины С к апофеме грани ADB, является перпендикуляром к плоскости ADB. </p>"
            "img" => array:1 [
              0 => array:5 [
                "name" => "260-1.jpg"
                "alt" => null
                "width" => "1545"
                "height" => 295
                "path" => "/media/geometrija_10/atanasjan-u23/0-00/260-1.webp?ts=1739436493"
              ]
            ]
          ]
          #changes: []
          #casts: []
          #classCastCache: []
          #attributeCastCache: []
          #dateFormat: null
          #appends: []
          #dispatchesEvents: []
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          #relations: []
          #touches: []
          +timestamps: true
          +usesUniqueIds: false
          #hidden: []
          #visible: []
          #fillable: []
          #guarded: array:1 [
            0 => "*"
          ]
        }
        1 => App\Models\Element {#1209
          #connection: "mysql"
          #table: "elements"
          #primaryKey: "id"
          #keyType: "int"
          +incrementing: true
          #with: []
          #withCount: []
          +preventsLazyLoading: false
          #perPage: 15
          +exists: true
          +wasRecentlyCreated: false
          #escapeWhenCastingToString: false
          #attributes: array:6 [
            "id" => 940865
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1219
              #items: array:1 [
                0 => App\Models\Edition {#1210
                  #connection: "mysql"
                  #table: "editions"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:21 [ …21]
                  #original: array:21 [ …21]
                  #changes: []
                  #casts: []
                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [ …1]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "task" => array:2 [
              "refs" => "744675"
              "type" => "task"
            ]
            "img" => array:2 [
              0 => array:5 [
                "name" => "260-1.png"
                "alt" => null
                "width" => "694"
                "height" => 2229
                "path" => "/media/geometrija_10/atanasjan-u23/2-00/260-1.webp?ts=1739441107"
              ]
              1 => array:5 [
                "name" => "260-2.png"
                "alt" => null
                "width" => "694"
                "height" => 2371
                "path" => "/media/geometrija_10/atanasjan-u23/2-00/260-2.webp?ts=1739441107"
              ]
            ]
          ]
          #original: array:6 [
            "id" => 940865
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1219}
            "task" => array:2 [
              "refs" => "744675"
              "type" => "task"
            ]
            "img" => array:2 [
              0 => array:5 [
                "name" => "260-1.png"
                "alt" => null
                "width" => "694"
                "height" => 2229
                "path" => "/media/geometrija_10/atanasjan-u23/2-00/260-1.webp?ts=1739441107"
              ]
              1 => array:5 [
                "name" => "260-2.png"
                "alt" => null
                "width" => "694"
                "height" => 2371
                "path" => "/media/geometrija_10/atanasjan-u23/2-00/260-2.webp?ts=1739441107"
              ]
            ]
          ]
          #changes: []
          #casts: []
          #classCastCache: []
          #attributeCastCache: []
          #dateFormat: null
          #appends: []
          #dispatchesEvents: []
          #observables: []
          #relations: []
          #touches: []
          +timestamps: true
          +usesUniqueIds: false
          #hidden: []
          #visible: []
          #fillable: []
          #guarded: array:1 [
            0 => "*"
          ]
        }
        2 => App\Models\Element {#1185
          #connection: "mysql"
          #table: "elements"
          #primaryKey: "id"
          #keyType: "int"
          +incrementing: true
          #with: []
          #withCount: []
          +preventsLazyLoading: false
          #perPage: 15
          +exists: true
          +wasRecentlyCreated: false
          #escapeWhenCastingToString: false
          #attributes: array:6 [
            "id" => 940608
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1195
              #items: array:1 [
                0 => App\Models\Edition {#1186
                  #connection: "mysql"
                  #table: "editions"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:21 [ …21]
                  #original: array:21 [ …21]
                  #changes: []
                  #casts: []
                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [ …1]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "task" => array:2 [
              "refs" => "744675"
              "type" => "task"
            ]
            "img" => array:1 [
              0 => array:5 [
                "name" => "260-1.jpg"
                "alt" => null
                "width" => "1300"
                "height" => 1120
                "path" => "/media/geometrija_10/atanasjan-u23/3-00/260-1.webp?ts=1739436728"
              ]
            ]
          ]
          #original: array:6 [
            "id" => 940608
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1195}
            "task" => array:2 [
              "refs" => "744675"
              "type" => "task"
            ]
            "img" => array:1 [
              0 => array:5 [
                "name" => "260-1.jpg"
                "alt" => null
                "width" => "1300"
                "height" => 1120
                "path" => "/media/geometrija_10/atanasjan-u23/3-00/260-1.webp?ts=1739436728"
              ]
            ]
          ]
          #changes: []
          #casts: []
          #classCastCache: []
          #attributeCastCache: []
          #dateFormat: null
          #appends: []
          #dispatchesEvents: []
          #observables: []
          #relations: []
          #touches: []
          +timestamps: true
          +usesUniqueIds: false
          #hidden: []
          #visible: []
          #fillable: []
          #guarded: array:1 [
            0 => "*"
          ]
        }
        3 => App\Models\Element {#1193
          #connection: "mysql"
          #table: "elements"
          #primaryKey: "id"
          #keyType: "int"
          +incrementing: true
          #with: []
          #withCount: []
          +preventsLazyLoading: false
          #perPage: 15
          +exists: true
          +wasRecentlyCreated: false
          #escapeWhenCastingToString: false
          #attributes: array:6 [
            "id" => 940663
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1203
              #items: array:1 [
                0 => App\Models\Edition {#1194
                  #connection: "mysql"
                  #table: "editions"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:21 [ …21]
                  #original: array:21 [ …21]
                  #changes: []
                  #casts: []
                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [ …1]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "task" => array:2 [
              "refs" => "744675"
              "type" => "task"
            ]
            "img" => array:1 [
              0 => array:5 [
                "name" => "260-1.jpg"
                "alt" => null
                "width" => "1148"
                "height" => 644
                "path" => "/media/geometrija_10/atanasjan-u23/4-00/260-1.webp?ts=1739436477"
              ]
            ]
          ]
          #original: array:6 [
            "id" => 940663
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1203}
            "task" => array:2 [
              "refs" => "744675"
              "type" => "task"
            ]
            "img" => array:1 [
              0 => array:5 [
                "name" => "260-1.jpg"
                "alt" => null
                "width" => "1148"
                "height" => 644
                "path" => "/media/geometrija_10/atanasjan-u23/4-00/260-1.webp?ts=1739436477"
              ]
            ]
          ]
          #changes: []
          #casts: []
          #classCastCache: []
          #attributeCastCache: []
          #dateFormat: null
          #appends: []
          #dispatchesEvents: []
          #observables: []
          #relations: []
          #touches: []
          +timestamps: true
          +usesUniqueIds: false
          #hidden: []
          #visible: []
          #fillable: []
          #guarded: array:1 [
            0 => "*"
          ]
        }
        4 => App\Models\Element {#1201
          #connection: "mysql"
          #table: "elements"
          #primaryKey: "id"
          #keyType: "int"
          +incrementing: true
          #with: []
          #withCount: []
          +preventsLazyLoading: false
          #perPage: 15
          +exists: true
          +wasRecentlyCreated: false
          #escapeWhenCastingToString: false
          #attributes: array:6 [
            "id" => 940808
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1211
              #items: array:1 [
                0 => App\Models\Edition {#1202
                  #connection: "mysql"
                  #table: "editions"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:21 [ …21]
                  #original: array:21 [ …21]
                  #changes: []
                  #casts: []
                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [ …1]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "task" => array:2 [
              "refs" => "744675"
              "type" => "task"
            ]
            "img" => array:1 [
              0 => array:5 [
                "name" => "260-1.jpg"
                "alt" => null
                "width" => "1329"
                "height" => 907
                "path" => "/media/geometrija_10/atanasjan-u23/5-00/260-1.webp?ts=1739436519"
              ]
            ]
          ]
          #original: array:6 [
            "id" => 940808
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1211}
            "task" => array:2 [
              "refs" => "744675"
              "type" => "task"
            ]
            "img" => array:1 [
              0 => array:5 [
                "name" => "260-1.jpg"
                "alt" => null
                "width" => "1329"
                "height" => 907
                "path" => "/media/geometrija_10/atanasjan-u23/5-00/260-1.webp?ts=1739436519"
              ]
            ]
          ]
          #changes: []
          #casts: []
          #classCastCache: []
          #attributeCastCache: []
          #dateFormat: null
          #appends: []
          #dispatchesEvents: []
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          #relations: []
          #touches: []
          +timestamps: true
          +usesUniqueIds: false
          #hidden: []
          #visible: []
          #fillable: []
          #guarded: array:1 [
            0 => "*"
          ]
        }
        5 => App\Models\Element {#1217
          #connection: "mysql"
          #table: "elements"
          #primaryKey: "id"
          #keyType: "int"
          +incrementing: true
          #with: []
          #withCount: []
          +preventsLazyLoading: false
          #perPage: 15
          +exists: true
          +wasRecentlyCreated: false
          #escapeWhenCastingToString: false
          #attributes: array:6 [
            "id" => 1351988
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1227
              #items: array:1 [
                0 => App\Models\Edition {#1218
                  #connection: "mysql"
                  #table: "editions"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
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            "text" => "<p><strong>а)</strong></p><p>По условию, $DABC$ — правильная треугольная пирамида, следовательно, её основание — равносторонний треугольник $ABC$, а высота $DO$ проецируется в центр этого треугольника — точку $O$. Плоскость $\alpha$ проходит через ребро $DC$ и высоту $DO$, значит, плоскость $\alpha$ — это плоскость $(DOC)$.</p><p>Для того чтобы доказать, что ребро $AB$ перпендикулярно плоскости $\alpha$, необходимо доказать, что ребро $AB$ перпендикулярно двум пересекающимся прямым, лежащим в этой плоскости. В качестве этих прямых возьмем $DO$ и $OC$.</p><ol><li>$DO$ — высота пирамиды, поэтому $DO$ перпендикулярна плоскости основания $(ABC)$. Так как прямая $AB$ лежит в плоскости основания, то $DO \perp AB$.</li> <li>В основании лежит равносторонний треугольник $ABC$, а точка $O$ — его центр. Проведем из вершины $C$ медиану $CM$ к стороне $AB$. В равностороннем треугольнике медиана является также и высотой, следовательно, $CM \perp AB$. Точка $O$ (центр треугольника) лежит на медиане $CM$, значит, прямая $OC$ является частью прямой $CM$. Таким образом, $OC \perp AB$.</li></ol><p>Мы получили, что прямая $AB$ перпендикулярна двум пересекающимся прямым $DO$ и $OC$ в плоскости $\alpha=(DOC)$. По признаку перпендикулярности прямой и плоскости, прямая $AB$ перпендикулярна плоскости $\alpha$. Что и требовалось доказать.</p><p><strong>Ответ:</strong> Доказано, что ребро $AB$ перпендикулярно к плоскости $\alpha$.</p><p><strong>б)</strong></p><p>Апофема грани $ADB$ — это высота, проведенная из вершины $D$ к стороне $AB$. Обозначим её $DM$, где $M$ — середина ребра $AB$.</p><p>Плоскость грани $ADB$ — это плоскость $(ADB)$.</p><p>Пусть $CH$ — перпендикуляр, проведённый из вершины $C$ к апофеме $DM$ (т.е. $CH \perp DM$, $H \in DM$). Нам нужно доказать, что $CH \perp (ADB)$. Для этого нужно доказать, что прямая $CH$ перпендикулярна двум пересекающимся прямым в плоскости $(ADB)$.</p><ol><li>По построению, $CH \perp DM$. Прямая $DM$ лежит в плоскости $(ADB)$.</li> <li>Рассмотрим плоскость $(DCM)$. Точки $D$, $C$, $M$ определяют эту плоскость. Так как $O$ лежит на $CM$, то плоскость $(DCM)$ совпадает с плоскостью $(DOC)$, то есть с плоскостью $\alpha$. В пункте <strong>а)</strong> мы доказали, что $AB \perp \alpha$, то есть $AB \perp (DCM)$.<br>Прямая $CH$ лежит в плоскости $(DCM)$, так как обе точки $C$ и $H$ (точка $H$ лежит на прямой $DM$, которая, в свою очередь, лежит в плоскости $(DCM)$) принадлежат этой плоскости.<br>Поскольку $AB \perp (DCM)$, то прямая $AB$ перпендикулярна любой прямой, лежащей в этой плоскости. Следовательно, $AB \perp CH$.</li></ol><p>Таким образом, прямая $CH$ перпендикулярна двум пересекающимся прямым $DM$ и $AB$ в плоскости $(ADB)$. Следовательно, по признаку перпендикулярности прямой и плоскости, прямая $CH$ перпендикулярна плоскости $(ADB)$. Что и требовалось доказать.</p><p><strong>Ответ:</strong> Доказано, что перпендикуляр, проведённый из вершины $C$ к апофеме грани $ADB$, является перпендикуляром к плоскости $ADB$.</p>"
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            "text" => "<p><strong>а)</strong></p><p>По условию, $DABC$ — правильная треугольная пирамида, следовательно, её основание — равносторонний треугольник $ABC$, а высота $DO$ проецируется в центр этого треугольника — точку $O$. Плоскость $\alpha$ проходит через ребро $DC$ и высоту $DO$, значит, плоскость $\alpha$ — это плоскость $(DOC)$.</p><p>Для того чтобы доказать, что ребро $AB$ перпендикулярно плоскости $\alpha$, необходимо доказать, что ребро $AB$ перпендикулярно двум пересекающимся прямым, лежащим в этой плоскости. В качестве этих прямых возьмем $DO$ и $OC$.</p><ol><li>$DO$ — высота пирамиды, поэтому $DO$ перпендикулярна плоскости основания $(ABC)$. Так как прямая $AB$ лежит в плоскости основания, то $DO \perp AB$.</li> <li>В основании лежит равносторонний треугольник $ABC$, а точка $O$ — его центр. Проведем из вершины $C$ медиану $CM$ к стороне $AB$. В равностороннем треугольнике медиана является также и высотой, следовательно, $CM \perp AB$. Точка $O$ (центр треугольника) лежит на медиане $CM$, значит, прямая $OC$ является частью прямой $CM$. Таким образом, $OC \perp AB$.</li></ol><p>Мы получили, что прямая $AB$ перпендикулярна двум пересекающимся прямым $DO$ и $OC$ в плоскости $\alpha=(DOC)$. По признаку перпендикулярности прямой и плоскости, прямая $AB$ перпендикулярна плоскости $\alpha$. Что и требовалось доказать.</p><p><strong>Ответ:</strong> Доказано, что ребро $AB$ перпендикулярно к плоскости $\alpha$.</p><p><strong>б)</strong></p><p>Апофема грани $ADB$ — это высота, проведенная из вершины $D$ к стороне $AB$. Обозначим её $DM$, где $M$ — середина ребра $AB$.</p><p>Плоскость грани $ADB$ — это плоскость $(ADB)$.</p><p>Пусть $CH$ — перпендикуляр, проведённый из вершины $C$ к апофеме $DM$ (т.е. $CH \perp DM$, $H \in DM$). Нам нужно доказать, что $CH \perp (ADB)$. Для этого нужно доказать, что прямая $CH$ перпендикулярна двум пересекающимся прямым в плоскости $(ADB)$.</p><ol><li>По построению, $CH \perp DM$. Прямая $DM$ лежит в плоскости $(ADB)$.</li> <li>Рассмотрим плоскость $(DCM)$. Точки $D$, $C$, $M$ определяют эту плоскость. Так как $O$ лежит на $CM$, то плоскость $(DCM)$ совпадает с плоскостью $(DOC)$, то есть с плоскостью $\alpha$. В пункте <strong>а)</strong> мы доказали, что $AB \perp \alpha$, то есть $AB \perp (DCM)$.<br>Прямая $CH$ лежит в плоскости $(DCM)$, так как обе точки $C$ и $H$ (точка $H$ лежит на прямой $DM$, которая, в свою очередь, лежит в плоскости $(DCM)$) принадлежат этой плоскости.<br>Поскольку $AB \perp (DCM)$, то прямая $AB$ перпендикулярна любой прямой, лежащей в этой плоскости. Следовательно, $AB \perp CH$.</li></ol><p>Таким образом, прямая $CH$ перпендикулярна двум пересекающимся прямым $DM$ и $AB$ в плоскости $(ADB)$. Следовательно, по признаку перпендикулярности прямой и плоскости, прямая $CH$ перпендикулярна плоскости $(ADB)$. Что и требовалось доказать.</p><p><strong>Ответ:</strong> Доказано, что перпендикуляр, проведённый из вершины $C$ к апофеме грани $ADB$, является перпендикуляром к плоскости $ADB$.</p>"
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                3 => App\Models\Term {#1225
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                4 => App\Models\Term {#1226
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            "field_city" => Illuminate\Database\Eloquent\Collection {#1233
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            "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1239
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                0 => App\Models\Term {#1240
                  #connection: "mysql"
                  #table: "terms"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
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                  #escapeWhenCastingToString: false
                  #attributes: array:10 [ …10]
                  #original: array:10 [ …10]
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                  #attributeCastCache: []
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                  #touches: []
                  +timestamps: true
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                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [ …1]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "field_publication_number" => "11"
            "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1241
              #items: array:1 [
                0 => App\Models\Term {#1242
                  #connection: "mysql"
                  #table: "terms"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
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                  #escapeWhenCastingToString: false
                  #attributes: array:6 [ …6]
                  #original: array:6 [ …6]
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                  #attributeCastCache: []
                  #dateFormat: null
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                  #relations: []
                  #touches: []
                  +timestamps: true
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                  #hidden: []
                  #visible: []
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                  #guarded: array:1 [ …1]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1243
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_under_the_edition_degree" => null
            "field_cover_description" => "с ромбами"
            "field_publication_year" => "2019"
            "field_publication_year_until" => null
            "field_part" => ""
            "field_part_writing" => ""
            "field_second_foreign_language" => null
            "field_for_whom" => "Учебник для общеобразовательных организаций"
            "field_allowed" => "Допущено Министерством просвещения Российской Федерации"
            "field_reserve_field" => "Математика: алгебра и начала математического анализа, геометрия"
            "field_link_to_source" => null
            "field_tasks_count" => "1147"
            "field_priority" => "12"
            "field_default_folder" => "/geometrija_10/atanasjan-u23/"
            "field_isbn" => "978-5-09-103606-0 (2023)"
            "field_cover" => array:1 [
              0 => "/media/geometrija_10/atanasjan-u23/covers/cover1.webp?ts=1739363242"
            ]
            "field_cover_alts" => array:1 [
              0 => ""
            ]
            "field_covers" => array:1 [
              0 => array:4 [
                "path" => "/media/geometrija_10/atanasjan-u23/covers/cover1.webp?ts=1739363242"
                "alt" => ""
                "width" => "1200"
                "height" => "1661"
              ]
            ]
            "field_popular_book" => null
            "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1244
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_new_book" => Illuminate\Database\Eloquent\Collection {#1245
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_old_book" => Illuminate\Database\Eloquent\Collection {#1246
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_url" => "/10-klass/geometrija/atanasjan-uchebnik"
            "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1247
              #items: array:1 [
                0 => App\Models\Term {#1248
                  #connection: "mysql"
                  #table: "terms"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
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                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:6 [ …6]
                  #original: array:6 [ …6]
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                  #attributeCastCache: []
                  #dateFormat: null
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                  #touches: []
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                }
              ]
              #escapeWhenCastingToString: false
            }
            "field_metatags_title" => null
            "field_metatags_description" => null
            "field_h1" => null
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            "field_description_bottom" => null
            "breadcrumbs" => array:3 [
              "class" => 381
              "subject" => 543
              "class_subject" => 392
            ]
          ]
          #original: array:50 [
            "id" => 36
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_tree_default_status" => "tasks"
            "field_pages_status" => null
            "field_subject" => Illuminate\Database\Eloquent\Collection {#1165}
            "field_class" => Illuminate\Database\Eloquent\Collection {#1175}
            "field_publisher" => Illuminate\Database\Eloquent\Collection {#1171}
            "field_author" => Illuminate\Database\Eloquent\Collection {#1169}
            "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1228}
            "field_book_type" => Illuminate\Database\Eloquent\Collection {#1229}
            "field_country" => Illuminate\Database\Eloquent\Collection {#1231}
            "field_city" => Illuminate\Database\Eloquent\Collection {#1233}
            "field_series" => Illuminate\Database\Eloquent\Collection {#1235}
            "field_umk" => Illuminate\Database\Eloquent\Collection {#1236}
            "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1237}
            "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1239}
            "field_publication_number" => "11"
            "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1241}
            "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1243}
            "field_under_the_edition_degree" => null
            "field_cover_description" => "с ромбами"
            "field_publication_year" => "2019"
            "field_publication_year_until" => null
            "field_part" => ""
            "field_part_writing" => ""
            "field_second_foreign_language" => null
            "field_for_whom" => "Учебник для общеобразовательных организаций"
            "field_allowed" => "Допущено Министерством просвещения Российской Федерации"
            "field_reserve_field" => "Математика: алгебра и начала математического анализа, геометрия"
            "field_link_to_source" => null
            "field_tasks_count" => "1147"
            "field_priority" => "12"
            "field_default_folder" => "/geometrija_10/atanasjan-u23/"
            "field_isbn" => "978-5-09-103606-0 (2023)"
            "field_cover" => array:1 [
              0 => "/media/geometrija_10/atanasjan-u23/covers/cover1.webp?ts=1739363242"
            ]
            "field_cover_alts" => array:1 [
              0 => ""
            ]
            "field_covers" => array:1 [
              0 => array:4 [
                "path" => "/media/geometrija_10/atanasjan-u23/covers/cover1.webp?ts=1739363242"
                "alt" => ""
                "width" => "1200"
                "height" => "1661"
              ]
            ]
            "field_popular_book" => null
            "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1244}
            "field_new_book" => Illuminate\Database\Eloquent\Collection {#1245}
            "field_old_book" => Illuminate\Database\Eloquent\Collection {#1246}
            "field_url" => "/10-klass/geometrija/atanasjan-uchebnik"
            "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1247}
            "field_metatags_title" => null
            "field_metatags_description" => null
            "field_h1" => null
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            "field_description_bottom" => null
            "breadcrumbs" => array:3 [
              "class" => 381
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              "class_subject" => 392
            ]
          ]
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          #guarded: array:1 [
            0 => "*"
          ]
        }
      ]
      #escapeWhenCastingToString: false
    }
    "page" => Illuminate\Database\Eloquent\Collection {#1256
      #items: array:1 [
        0 => App\Models\BookPage {#1255
          #connection: "mysql"
          #table: "book_pages"
          #primaryKey: "id"
          #keyType: "int"
          +incrementing: true
          #with: []
          #withCount: []
          +preventsLazyLoading: false
          #perPage: 15
          +exists: true
          +wasRecentlyCreated: false
          #escapeWhenCastingToString: false
          #attributes: array:21 [
            "id" => 933859
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_page_start" => "77"
            "field_url" => "/10-klass/geometrija/atanasjan-uchebnik/page-77"
            "field_display_title" => "77"
            "field_folder" => "1"
            "field_image_name" => "77"
            "field_branch_parent" => Illuminate\Database\Eloquent\Collection {#1257
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_weight" => "0"
            "field_book_parent" => Illuminate\Database\Eloquent\Collection {#1258
              #items: array:1 [
                0 => App\Models\Book {#1176}
              ]
              #escapeWhenCastingToString: false
            }
            "field_metatags_title" => null
            "field_metatags_description" => null
            "field_h1" => null
            "field_description_top" => null
            "field_description_bottom" => null
            "edition_groups" => Illuminate\Database\Eloquent\Collection {#1259
              #items: []
              #escapeWhenCastingToString: false
            }
            "content" => Illuminate\Database\Eloquent\Collection {#1269
              #items: array:1 [
                0 => App\Models\Element {#1268
                  #connection: "mysql"
                  #table: "elements"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: true
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:6 [ …6]
                  #original: array:6 [ …6]
                  #changes: []
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                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [ …1]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "next" => array:2 [
              "refs" => "933860"
              "type" => "book_page"
            ]
            "previous" => array:2 [
              "refs" => "933858"
              "type" => "book_page"
            ]
            "tasks" => Illuminate\Database\Eloquent\Collection {#1482
              #items: array:12 [
                0 => App\Models\Task {#1500
                  #connection: "mysql"
                  #table: "tasks"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: true
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:24 [ …24]
                  #original: array:24 [ …24]
                  #changes: []
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                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
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                  #dispatchesEvents: []
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                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [ …1]
                }
                1 => App\Models\Task {#1507
                  #connection: "mysql"
                  #table: "tasks"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: true
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:24 [ …24]
                  #original: array:24 [ …24]
                  #changes: []
                  #casts: []
                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [ …1]
                }
                2 => App\Models\Task {#1510
                  #connection: "mysql"
                  #table: "tasks"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: true
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:24 [ …24]
                  #original: array:24 [ …24]
                  #changes: []
                  #casts: []
                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [ …1]
                }
                3 => App\Models\Task {#1509
                  #connection: "mysql"
                  #table: "tasks"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: true
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:24 [ …24]
                  #original: array:24 [ …24]
                  #changes: []
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                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [ …1]
                }
                4 => App\Models\Task {#1511
                  #connection: "mysql"
                  #table: "tasks"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: true
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:24 [ …24]
                  #original: array:24 [ …24]
                  #changes: []
                  #casts: []
                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [ …1]
                }
                5 => App\Models\Task {#1531
                  #connection: "mysql"
                  #table: "tasks"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: true
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:24 [ …24]
                  #original: array:24 [ …24]
                  #changes: []
                  #casts: []
                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [ …1]
                }
                6 => App\Models\Task {#1551
                  #connection: "mysql"
                  #table: "tasks"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: true
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:24 [ …24]
                  #original: array:24 [ …24]
                  #changes: []
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                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
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                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [ …1]
                }
                7 => App\Models\Task {#1571
                  #connection: "mysql"
                  #table: "tasks"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: true
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:24 [ …24]
                  #original: array:24 [ …24]
                  #changes: []
                  #casts: []
                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [ …1]
                }
                8 => App\Models\Task {#1591
                  #connection: "mysql"
                  #table: "tasks"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: true
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:24 [ …24]
                  #original: array:24 [ …24]
                  #changes: []
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                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [ …1]
                }
                9 => App\Models\Task {#1654
                  #connection: "mysql"
                  #table: "tasks"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: true
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:24 [ …24]
                  #original: array:24 [ …24]
                  #changes: []
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                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
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                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [ …1]
                }
                10 => App\Models\Task {#1657
                  #connection: "mysql"
                  #table: "tasks"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: true
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:24 [ …24]
                  #original: array:24 [ …24]
                  #changes: []
                  #casts: []
                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [ …1]
                }
                11 => App\Models\Task {#1656
                  #connection: "mysql"
                  #table: "tasks"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: true
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:24 [ …24]
                  #original: array:24 [ …24]
                  #changes: []
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                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
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                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [ …1]
                }
              ]
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:21 [
            "id" => 933859
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_page_start" => "77"
            "field_url" => "/10-klass/geometrija/atanasjan-uchebnik/page-77"
            "field_display_title" => "77"
            "field_folder" => "1"
            "field_image_name" => "77"
            "field_branch_parent" => Illuminate\Database\Eloquent\Collection {#1257}
            "field_weight" => "0"
            "field_book_parent" => Illuminate\Database\Eloquent\Collection {#1258}
            "field_metatags_title" => null
            "field_metatags_description" => null
            "field_h1" => null
            "field_description_top" => null
            "field_description_bottom" => null
            "edition_groups" => Illuminate\Database\Eloquent\Collection {#1259}
            "content" => Illuminate\Database\Eloquent\Collection {#1269}
            "next" => array:2 [
              "refs" => "933860"
              "type" => "book_page"
            ]
            "previous" => array:2 [
              "refs" => "933858"
              "type" => "book_page"
            ]
            "tasks" => Illuminate\Database\Eloquent\Collection {#1482}
          ]
          #changes: []
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№260 (с. 77)
Условие. №260 (с. 77)
скриншот условия
Геометрия, 10-11 класс Учебник, авторы: Атанасян Левон Сергеевич, Бутузов Валентин Фёдорович, Кадомцев Сергей Борисович, Позняк Эдуард Генрихович, Киселёва Людмила Сергеевна, издательство Просвещение, Москва, 2019, коричневого цвета, страница 77, номер 260, Условие

260. В правильной треугольной пирамиде DABC через боковое ребро DC и высоту DO пирамиды проведена плоскость α. Докажите, что: а) ребро AB перпендикулярно к плоскости α; б) перпендикуляр, проведённый из вершины С к апофеме грани ADB, является перпендикуляром к плоскости ADB.

Решение 2. №260 (с. 77)
Геометрия, 10-11 класс Учебник, авторы: Атанасян Левон Сергеевич, Бутузов Валентин Фёдорович, Кадомцев Сергей Борисович, Позняк Эдуард Генрихович, Киселёва Людмила Сергеевна, издательство Просвещение, Москва, 2019, коричневого цвета, страница 77, номер 260, Решение 2
Геометрия, 10-11 класс Учебник, авторы: Атанасян Левон Сергеевич, Бутузов Валентин Фёдорович, Кадомцев Сергей Борисович, Позняк Эдуард Генрихович, Киселёва Людмила Сергеевна, издательство Просвещение, Москва, 2019, коричневого цвета, страница 77, номер 260, Решение 2 (продолжение 2)
Решение 3. №260 (с. 77)
Геометрия, 10-11 класс Учебник, авторы: Атанасян Левон Сергеевич, Бутузов Валентин Фёдорович, Кадомцев Сергей Борисович, Позняк Эдуард Генрихович, Киселёва Людмила Сергеевна, издательство Просвещение, Москва, 2019, коричневого цвета, страница 77, номер 260, Решение 3
Решение 4. №260 (с. 77)
Геометрия, 10-11 класс Учебник, авторы: Атанасян Левон Сергеевич, Бутузов Валентин Фёдорович, Кадомцев Сергей Борисович, Позняк Эдуард Генрихович, Киселёва Людмила Сергеевна, издательство Просвещение, Москва, 2019, коричневого цвета, страница 77, номер 260, Решение 4
Решение 5. №260 (с. 77)
Решение 6. №260 (с. 77)

а)

По условию, $DABC$ — правильная треугольная пирамида, следовательно, её основание — равносторонний треугольник $ABC$, а высота $DO$ проецируется в центр этого треугольника — точку $O$. Плоскость $\alpha$ проходит через ребро $DC$ и высоту $DO$, значит, плоскость $\alpha$ — это плоскость $(DOC)$.

Для того чтобы доказать, что ребро $AB$ перпендикулярно плоскости $\alpha$, необходимо доказать, что ребро $AB$ перпендикулярно двум пересекающимся прямым, лежащим в этой плоскости. В качестве этих прямых возьмем $DO$ и $OC$.

  1. $DO$ — высота пирамиды, поэтому $DO$ перпендикулярна плоскости основания $(ABC)$. Так как прямая $AB$ лежит в плоскости основания, то $DO \perp AB$.
  2. В основании лежит равносторонний треугольник $ABC$, а точка $O$ — его центр. Проведем из вершины $C$ медиану $CM$ к стороне $AB$. В равностороннем треугольнике медиана является также и высотой, следовательно, $CM \perp AB$. Точка $O$ (центр треугольника) лежит на медиане $CM$, значит, прямая $OC$ является частью прямой $CM$. Таким образом, $OC \perp AB$.

Мы получили, что прямая $AB$ перпендикулярна двум пересекающимся прямым $DO$ и $OC$ в плоскости $\alpha=(DOC)$. По признаку перпендикулярности прямой и плоскости, прямая $AB$ перпендикулярна плоскости $\alpha$. Что и требовалось доказать.

Ответ: Доказано, что ребро $AB$ перпендикулярно к плоскости $\alpha$.

б)

Апофема грани $ADB$ — это высота, проведенная из вершины $D$ к стороне $AB$. Обозначим её $DM$, где $M$ — середина ребра $AB$.

Плоскость грани $ADB$ — это плоскость $(ADB)$.

Пусть $CH$ — перпендикуляр, проведённый из вершины $C$ к апофеме $DM$ (т.е. $CH \perp DM$, $H \in DM$). Нам нужно доказать, что $CH \perp (ADB)$. Для этого нужно доказать, что прямая $CH$ перпендикулярна двум пересекающимся прямым в плоскости $(ADB)$.

  1. По построению, $CH \perp DM$. Прямая $DM$ лежит в плоскости $(ADB)$.
  2. Рассмотрим плоскость $(DCM)$. Точки $D$, $C$, $M$ определяют эту плоскость. Так как $O$ лежит на $CM$, то плоскость $(DCM)$ совпадает с плоскостью $(DOC)$, то есть с плоскостью $\alpha$. В пункте а) мы доказали, что $AB \perp \alpha$, то есть $AB \perp (DCM)$.
    Прямая $CH$ лежит в плоскости $(DCM)$, так как обе точки $C$ и $H$ (точка $H$ лежит на прямой $DM$, которая, в свою очередь, лежит в плоскости $(DCM)$) принадлежат этой плоскости.
    Поскольку $AB \perp (DCM)$, то прямая $AB$ перпендикулярна любой прямой, лежащей в этой плоскости. Следовательно, $AB \perp CH$.

Таким образом, прямая $CH$ перпендикулярна двум пересекающимся прямым $DM$ и $AB$ в плоскости $(ADB)$. Следовательно, по признаку перпендикулярности прямой и плоскости, прямая $CH$ перпендикулярна плоскости $(ADB)$. Что и требовалось доказать.

Ответ: Доказано, что перпендикуляр, проведённый из вершины $C$ к апофеме грани $ADB$, является перпендикуляром к плоскости $ADB$.

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Мы подготовили для вас ответ c подробным объяснением домашего задания по геометрии за 10-11 класс, для упражнения номер 260 расположенного на странице 77 к учебнику 2019 года издания для учащихся школ и гимназий.

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