Номер 304, страница 87 - 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 3. Правильные многогранники, дополнительные задачи - номер 304, страница 87.

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                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:6 [ …6]
                          #original: array:6 [ …6]
                          #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_author" => Illuminate\Database\Eloquent\Collection {#1139
                      #items: array:5 [
                        0 => App\Models\Term {#1140
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:12 [ …12]
                          #original: array:12 [ …12]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [ …1]
                        }
                        1 => App\Models\Term {#1141
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:12 [ …12]
                          #original: array:12 [ …12]
                          #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\Term {#1142
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:12 [ …12]
                          #original: array:12 [ …12]
                          #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\Term {#1143
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:12 [ …12]
                          #original: array:12 [ …12]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [ …1]
                        }
                        4 => App\Models\Term {#1144
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:12 [ …12]
                          #original: array:12 [ …12]
                          #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_author_foreign" => Illuminate\Database\Eloquent\Collection {#1145
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_book_type" => Illuminate\Database\Eloquent\Collection {#1146
                      #items: array:1 [
                        0 => App\Models\Term {#1147
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:10 [ …10]
                          #original: array:10 [ …10]
                          #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_country" => Illuminate\Database\Eloquent\Collection {#1148
                      #items: array:1 [
                        0 => App\Models\Term {#1149
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:6 [ …6]
                          #original: array:6 [ …6]
                          #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_city" => Illuminate\Database\Eloquent\Collection {#1150
                      #items: array:1 [
                        0 => App\Models\Term {#1151
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:6 [ …6]
                          #original: array:6 [ …6]
                          #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_series" => Illuminate\Database\Eloquent\Collection {#1152
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_umk" => Illuminate\Database\Eloquent\Collection {#1153
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1154
                      #items: array:1 [
                        0 => App\Models\Term {#1155
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:6 [ …6]
                          #original: array:6 [ …6]
                          #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_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1156
                      #items: array:1 [
                        0 => App\Models\Term {#1157
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:10 [ …10]
                          #original: array:10 [ …10]
                          #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_publication_number" => "11"
                    "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1158
                      #items: array:1 [
                        0 => App\Models\Term {#1159
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:6 [ …6]
                          #original: array:6 [ …6]
                          #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_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1160
                      #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 {#1161
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_new_book" => Illuminate\Database\Eloquent\Collection {#1162
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_old_book" => Illuminate\Database\Eloquent\Collection {#1163
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_url" => "/10-klass/geometrija/atanasjan-uchebnik"
                    "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1164
                      #items: array:1 [
                        0 => App\Models\Term {#1165
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:6 [ …6]
                          #original: array:6 [ …6]
                          #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_metatags_title" => null
                    "field_metatags_description" => null
                    "field_h1" => null
                    "field_description_top" => null
                    "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 {#1133}
                    "field_class" => Illuminate\Database\Eloquent\Collection {#1134}
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1137}
                    "field_author" => Illuminate\Database\Eloquent\Collection {#1139}
                    "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1145}
                    "field_book_type" => Illuminate\Database\Eloquent\Collection {#1146}
                    "field_country" => Illuminate\Database\Eloquent\Collection {#1148}
                    "field_city" => Illuminate\Database\Eloquent\Collection {#1150}
                    "field_series" => Illuminate\Database\Eloquent\Collection {#1152}
                    "field_umk" => Illuminate\Database\Eloquent\Collection {#1153}
                    "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1154}
                    "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1156}
                    "field_publication_number" => "11"
                    "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1158}
                    "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1160}
                    "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 {#1161}
                    "field_new_book" => Illuminate\Database\Eloquent\Collection {#1162}
                    "field_old_book" => Illuminate\Database\Eloquent\Collection {#1163}
                    "field_url" => "/10-klass/geometrija/atanasjan-uchebnik"
                    "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1164}
                    "field_metatags_title" => null
                    "field_metatags_description" => null
                    "field_h1" => null
                    "field_description_top" => null
                    "field_description_bottom" => null
                    "breadcrumbs" => array:3 [
                      "class" => 381
                      "subject" => 543
                      "class_subject" => 392
                    ]
                  ]
                  #changes: []
                  #casts: []
                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [
                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1166
              #items: []
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 744380
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Многогранники"
            "field_branch_order" => "3"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1132}
            "field_page_start" => "63"
            "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 {#1168}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1166}
          ]
          #changes: []
          #casts: []
          #classCastCache: []
          #attributeCastCache: []
          #dateFormat: null
          #appends: []
          #dispatchesEvents: []
          #observables: []
          #relations: []
          #touches: []
          +timestamps: true
          +usesUniqueIds: false
          #hidden: []
          #visible: []
          #fillable: []
          #guarded: array:1 [
            0 => "*"
          ]
        }
        1 => App\Models\Branch {#1167
          #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" => 744385
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Правильные многогранники, дополнительные задачи"
            "field_branch_order" => "3"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1172
              #items: array:1 [
                0 => App\Models\Term {#1169
                  #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 [
                    "id" => 32
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "Параграф"
                    "field_cases" => array:6 [ …6]
                    "field_page_check_not_needed" => null
                    "field_short_name" => "§"
                  ]
                  #original: array:7 [
                    "id" => 32
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "Параграф"
                    "field_cases" => array:6 [ …6]
                    "field_page_check_not_needed" => null
                    "field_short_name" => "§"
                  ]
                  #changes: []
                  #casts: []
                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
                  #observables: []
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            "text" => "<p> <b>304.</b> В правильной четырёхугольной пирамиде плоский угол при вершине равен 60°. Докажите, что двугранный угол между боковой гранью и основанием пирамиды вдвое меньше двугранного угла при боковом ребре. </p>"
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            "edition" => Illuminate\Database\Eloquent\Collection {#1187
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                0 => App\Models\Edition {#1178
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            "text" => "<p>Пусть дана правильная четырехугольная пирамида $SABCD$, где $S$ — вершина, а $ABCD$ — квадратное основание. По условию, плоский угол при вершине равен $60^\circ$. Это означает, что угол в каждой боковой грани при вершине $S$ равен $60^\circ$, например, $\angle ASB = 60^\circ$.</p><p>Так как пирамида правильная, ее боковые грани — равные равнобедренные треугольники. В нашем случае, $\triangle ASB$ является равнобедренным с $SA = SB$. Поскольку угол при вершине $\angle ASB = 60^\circ$, то углы при основании этого треугольника также равны $(180^\circ - 60^\circ) / 2 = 60^\circ$. Следовательно, все боковые грани пирамиды являются равносторонними треугольниками. Это означает, что все ребра пирамиды равны. Обозначим длину ребра за $a$: $AB = BC = CD = DA = SA = SB = SC = SD = a$.</p><p><strong>Нахождение двугранного угла между боковой гранью и основанием</strong></p><p>Пусть $\alpha$ — двугранный угол между боковой гранью, например, $(SBC)$, и основанием $(ABCD)$. Этот угол измеряется линейным углом, образованным двумя перпендикулярами, проведенными к линии их пересечения, то есть к ребру $BC$.</p><p>Проведем апофему $SM$ в грани $SBC$. Так как $\triangle SBC$ — равносторонний, $SM$ является его высотой и медианой, поэтому $M$ — середина $BC$ и $SM \perp BC$. Высота равностороннего треугольника со стороной $a$ равна $SM = \frac{a\sqrt{3}}{2}$.</p><p>Пусть $O$ — центр основания (точка пересечения диагоналей квадрата). Проведем отрезок $OM$. Так как $ABCD$ — квадрат, $OM$ является средней линией $\triangle ABC$ или $\triangle DBC$ (в зависимости от расположения), и $OM \perp BC$. Длина $OM$ равна половине стороны квадрата: $OM = \frac{1}{2}AB = \frac{a}{2}$.</p><p>Поскольку $SM \perp BC$ и $OM \perp BC$, то $\angle SMO$ — это линейный угол двугранного угла $\alpha$. Рассмотрим прямоугольный треугольник $\triangle SOM$ (где $\angle SOM = 90^\circ$, так как $SO$ — высота пирамиды).</p><p>Найдем косинус угла $\alpha = \angle SMO$:</p><p>$\cos \alpha = \frac{OM}{SM} = \frac{a/2}{a\sqrt{3}/2} = \frac{1}{\sqrt{3}}$.</p><p><strong>Нахождение двугранного угла при боковом ребре</strong></p><p>Пусть $\beta$ — двугранный угол при боковом ребре, например, при ребре $SB$. Этот угол образован двумя смежными боковыми гранями $(SAB)$ и $(SBC)$.</p><p>Для нахождения этого угла построим его линейный угол. Проведем в гранях $(SAB)$ и $(SBC)$ перпендикуляры к общему ребру $SB$.</p><p>В равностороннем треугольнике $\triangle SAB$ проведем высоту $AH$ к стороне $SB$. Длина этой высоты равна $AH = \frac{a\sqrt{3}}{2}$.</p><p>В равностороннем треугольнике $\triangle SBC$ проведем высоту $CH$ к стороне $SB$. Длина этой высоты равна $CH = \frac{a\sqrt{3}}{2}$.</p><p>Тогда $\angle AHC$ является линейным углом двугранного угла $\beta$. Рассмотрим треугольник $\triangle AHC$. Мы знаем длины его сторон: $AH = CH = \frac{a\sqrt{3}}{2}$. Третья сторона, $AC$, является диагональю квадрата $ABCD$, ее длина $AC = a\sqrt{2}$.</p><p>Применим к треугольнику $\triangle AHC$ теорему косинусов для нахождения угла $\beta = \angle AHC$:</p><p>$AC^2 = AH^2 + CH^2 - 2 \cdot AH \cdot CH \cdot \cos\beta$</p><p>$(a\sqrt{2})^2 = (\frac{a\sqrt{3}}{2})^2 + (\frac{a\sqrt{3}}{2})^2 - 2 \cdot \frac{a\sqrt{3}}{2} \cdot \frac{a\sqrt{3}}{2} \cdot \cos\beta$</p><p>$2a^2 = \frac{3a^2}{4} + \frac{3a^2}{4} - 2 \cdot \frac{3a^2}{4} \cdot \cos\beta$</p><p>$2a^2 = \frac{6a^2}{4} - \frac{6a^2}{4} \cdot \cos\beta$</p><p>$2a^2 = \frac{3a^2}{2} - \frac{3a^2}{2} \cdot \cos\beta$</p><p>Разделим обе части уравнения на $a^2$ (так как $a \neq 0$):</p><p>$2 = \frac{3}{2} - \frac{3}{2} \cos\beta$</p><p>$2 - \frac{3}{2} = - \frac{3}{2} \cos\beta$</p><p>$\frac{1}{2} = - \frac{3}{2} \cos\beta$</p><p>$\cos\beta = -\frac{1}{3}$.</p><p><strong>Доказательство</strong></p><p>Мы получили значения косинусов для обоих углов: $\cos \alpha = \frac{1}{\sqrt{3}}$ и $\cos\beta = -\frac{1}{3}$. Нам нужно доказать, что $\alpha = \frac{\beta}{2}$, что эквивалентно $\beta = 2\alpha$.</p><p>Воспользуемся формулой косинуса двойного угла: $\cos(2\alpha) = 2\cos^2\alpha - 1$.</p><p>Подставим найденное значение $\cos\alpha$:</p><p>$\cos(2\alpha) = 2 \cdot (\frac{1}{\sqrt{3}})^2 - 1 = 2 \cdot \frac{1}{3} - 1 = \frac{2}{3} - 1 = -\frac{1}{3}$.</p><p>Таким образом, мы получили, что $\cos(2\alpha) = -\frac{1}{3}$, и мы также знаем, что $\cos\beta = -\frac{1}{3}$. Следовательно, $\cos(2\alpha) = \cos\beta$.</p><p>Поскольку $\alpha$ — угол между плоскостью боковой грани и основанием, он острый ($0 &lt; \alpha &lt; 90^\circ$). Значит, $0 &lt; 2\alpha &lt; 180^\circ$. Угол $\beta$ — двугранный угол в пирамиде, он также находится в диапазоне $0 &lt; \beta &lt; 180^\circ$. Из равенства $\cos(2\alpha) = \cos\beta$ на этом интервале следует, что $2\alpha = \beta$.</p><p>Это доказывает, что двугранный угол между боковой гранью и основанием пирамиды ($\alpha$) вдвое меньше двугранного угла при боковом ребре ($\beta$).</p><p><strong>Ответ:</strong> Утверждение доказано. Мы показали, что $\cos \alpha = \frac{1}{\sqrt{3}}$ и $\cos \beta = -\frac{1}{3}$, а из формулы двойного угла $\cos(2\alpha) = 2\cos^2\alpha - 1$ следует, что $\cos(2\alpha) = \cos\beta$, откуда $2\alpha = \beta$.</p>"
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            "text" => "<p>Пусть дана правильная четырехугольная пирамида $SABCD$, где $S$ — вершина, а $ABCD$ — квадратное основание. По условию, плоский угол при вершине равен $60^\circ$. Это означает, что угол в каждой боковой грани при вершине $S$ равен $60^\circ$, например, $\angle ASB = 60^\circ$.</p><p>Так как пирамида правильная, ее боковые грани — равные равнобедренные треугольники. В нашем случае, $\triangle ASB$ является равнобедренным с $SA = SB$. Поскольку угол при вершине $\angle ASB = 60^\circ$, то углы при основании этого треугольника также равны $(180^\circ - 60^\circ) / 2 = 60^\circ$. Следовательно, все боковые грани пирамиды являются равносторонними треугольниками. Это означает, что все ребра пирамиды равны. Обозначим длину ребра за $a$: $AB = BC = CD = DA = SA = SB = SC = SD = a$.</p><p><strong>Нахождение двугранного угла между боковой гранью и основанием</strong></p><p>Пусть $\alpha$ — двугранный угол между боковой гранью, например, $(SBC)$, и основанием $(ABCD)$. Этот угол измеряется линейным углом, образованным двумя перпендикулярами, проведенными к линии их пересечения, то есть к ребру $BC$.</p><p>Проведем апофему $SM$ в грани $SBC$. Так как $\triangle SBC$ — равносторонний, $SM$ является его высотой и медианой, поэтому $M$ — середина $BC$ и $SM \perp BC$. Высота равностороннего треугольника со стороной $a$ равна $SM = \frac{a\sqrt{3}}{2}$.</p><p>Пусть $O$ — центр основания (точка пересечения диагоналей квадрата). Проведем отрезок $OM$. Так как $ABCD$ — квадрат, $OM$ является средней линией $\triangle ABC$ или $\triangle DBC$ (в зависимости от расположения), и $OM \perp BC$. Длина $OM$ равна половине стороны квадрата: $OM = \frac{1}{2}AB = \frac{a}{2}$.</p><p>Поскольку $SM \perp BC$ и $OM \perp BC$, то $\angle SMO$ — это линейный угол двугранного угла $\alpha$. Рассмотрим прямоугольный треугольник $\triangle SOM$ (где $\angle SOM = 90^\circ$, так как $SO$ — высота пирамиды).</p><p>Найдем косинус угла $\alpha = \angle SMO$:</p><p>$\cos \alpha = \frac{OM}{SM} = \frac{a/2}{a\sqrt{3}/2} = \frac{1}{\sqrt{3}}$.</p><p><strong>Нахождение двугранного угла при боковом ребре</strong></p><p>Пусть $\beta$ — двугранный угол при боковом ребре, например, при ребре $SB$. Этот угол образован двумя смежными боковыми гранями $(SAB)$ и $(SBC)$.</p><p>Для нахождения этого угла построим его линейный угол. Проведем в гранях $(SAB)$ и $(SBC)$ перпендикуляры к общему ребру $SB$.</p><p>В равностороннем треугольнике $\triangle SAB$ проведем высоту $AH$ к стороне $SB$. Длина этой высоты равна $AH = \frac{a\sqrt{3}}{2}$.</p><p>В равностороннем треугольнике $\triangle SBC$ проведем высоту $CH$ к стороне $SB$. Длина этой высоты равна $CH = \frac{a\sqrt{3}}{2}$.</p><p>Тогда $\angle AHC$ является линейным углом двугранного угла $\beta$. Рассмотрим треугольник $\triangle AHC$. Мы знаем длины его сторон: $AH = CH = \frac{a\sqrt{3}}{2}$. Третья сторона, $AC$, является диагональю квадрата $ABCD$, ее длина $AC = a\sqrt{2}$.</p><p>Применим к треугольнику $\triangle AHC$ теорему косинусов для нахождения угла $\beta = \angle AHC$:</p><p>$AC^2 = AH^2 + CH^2 - 2 \cdot AH \cdot CH \cdot \cos\beta$</p><p>$(a\sqrt{2})^2 = (\frac{a\sqrt{3}}{2})^2 + (\frac{a\sqrt{3}}{2})^2 - 2 \cdot \frac{a\sqrt{3}}{2} \cdot \frac{a\sqrt{3}}{2} \cdot \cos\beta$</p><p>$2a^2 = \frac{3a^2}{4} + \frac{3a^2}{4} - 2 \cdot \frac{3a^2}{4} \cdot \cos\beta$</p><p>$2a^2 = \frac{6a^2}{4} - \frac{6a^2}{4} \cdot \cos\beta$</p><p>$2a^2 = \frac{3a^2}{2} - \frac{3a^2}{2} \cdot \cos\beta$</p><p>Разделим обе части уравнения на $a^2$ (так как $a \neq 0$):</p><p>$2 = \frac{3}{2} - \frac{3}{2} \cos\beta$</p><p>$2 - \frac{3}{2} = - \frac{3}{2} \cos\beta$</p><p>$\frac{1}{2} = - \frac{3}{2} \cos\beta$</p><p>$\cos\beta = -\frac{1}{3}$.</p><p><strong>Доказательство</strong></p><p>Мы получили значения косинусов для обоих углов: $\cos \alpha = \frac{1}{\sqrt{3}}$ и $\cos\beta = -\frac{1}{3}$. Нам нужно доказать, что $\alpha = \frac{\beta}{2}$, что эквивалентно $\beta = 2\alpha$.</p><p>Воспользуемся формулой косинуса двойного угла: $\cos(2\alpha) = 2\cos^2\alpha - 1$.</p><p>Подставим найденное значение $\cos\alpha$:</p><p>$\cos(2\alpha) = 2 \cdot (\frac{1}{\sqrt{3}})^2 - 1 = 2 \cdot \frac{1}{3} - 1 = \frac{2}{3} - 1 = -\frac{1}{3}$.</p><p>Таким образом, мы получили, что $\cos(2\alpha) = -\frac{1}{3}$, и мы также знаем, что $\cos\beta = -\frac{1}{3}$. Следовательно, $\cos(2\alpha) = \cos\beta$.</p><p>Поскольку $\alpha$ — угол между плоскостью боковой грани и основанием, он острый ($0 &lt; \alpha &lt; 90^\circ$). Значит, $0 &lt; 2\alpha &lt; 180^\circ$. Угол $\beta$ — двугранный угол в пирамиде, он также находится в диапазоне $0 &lt; \beta &lt; 180^\circ$. Из равенства $\cos(2\alpha) = \cos\beta$ на этом интервале следует, что $2\alpha = \beta$.</p><p>Это доказывает, что двугранный угол между боковой гранью и основанием пирамиды ($\alpha$) вдвое меньше двугранного угла при боковом ребре ($\beta$).</p><p><strong>Ответ:</strong> Утверждение доказано. Мы показали, что $\cos \alpha = \frac{1}{\sqrt{3}}$ и $\cos \beta = -\frac{1}{3}$, а из формулы двойного угла $\cos(2\alpha) = 2\cos^2\alpha - 1$ следует, что $\cos(2\alpha) = \cos\beta$, откуда $2\alpha = \beta$.</p>"
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№304 (с. 87)
Условие. №304 (с. 87)
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 87, номер 304, Условие

304. В правильной четырёхугольной пирамиде плоский угол при вершине равен 60°. Докажите, что двугранный угол между боковой гранью и основанием пирамиды вдвое меньше двугранного угла при боковом ребре.

Решение 2. №304 (с. 87)
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 87, номер 304, Решение 2
Решение 3. №304 (с. 87)
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 87, номер 304, Решение 3
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 87, номер 304, Решение 3 (продолжение 2)
Решение 5. №304 (с. 87)
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 87, номер 304, Решение 5
Решение 6. №304 (с. 87)

Пусть дана правильная четырехугольная пирамида $SABCD$, где $S$ — вершина, а $ABCD$ — квадратное основание. По условию, плоский угол при вершине равен $60^\circ$. Это означает, что угол в каждой боковой грани при вершине $S$ равен $60^\circ$, например, $\angle ASB = 60^\circ$.

Так как пирамида правильная, ее боковые грани — равные равнобедренные треугольники. В нашем случае, $\triangle ASB$ является равнобедренным с $SA = SB$. Поскольку угол при вершине $\angle ASB = 60^\circ$, то углы при основании этого треугольника также равны $(180^\circ - 60^\circ) / 2 = 60^\circ$. Следовательно, все боковые грани пирамиды являются равносторонними треугольниками. Это означает, что все ребра пирамиды равны. Обозначим длину ребра за $a$: $AB = BC = CD = DA = SA = SB = SC = SD = a$.

Нахождение двугранного угла между боковой гранью и основанием

Пусть $\alpha$ — двугранный угол между боковой гранью, например, $(SBC)$, и основанием $(ABCD)$. Этот угол измеряется линейным углом, образованным двумя перпендикулярами, проведенными к линии их пересечения, то есть к ребру $BC$.

Проведем апофему $SM$ в грани $SBC$. Так как $\triangle SBC$ — равносторонний, $SM$ является его высотой и медианой, поэтому $M$ — середина $BC$ и $SM \perp BC$. Высота равностороннего треугольника со стороной $a$ равна $SM = \frac{a\sqrt{3}}{2}$.

Пусть $O$ — центр основания (точка пересечения диагоналей квадрата). Проведем отрезок $OM$. Так как $ABCD$ — квадрат, $OM$ является средней линией $\triangle ABC$ или $\triangle DBC$ (в зависимости от расположения), и $OM \perp BC$. Длина $OM$ равна половине стороны квадрата: $OM = \frac{1}{2}AB = \frac{a}{2}$.

Поскольку $SM \perp BC$ и $OM \perp BC$, то $\angle SMO$ — это линейный угол двугранного угла $\alpha$. Рассмотрим прямоугольный треугольник $\triangle SOM$ (где $\angle SOM = 90^\circ$, так как $SO$ — высота пирамиды).

Найдем косинус угла $\alpha = \angle SMO$:

$\cos \alpha = \frac{OM}{SM} = \frac{a/2}{a\sqrt{3}/2} = \frac{1}{\sqrt{3}}$.

Нахождение двугранного угла при боковом ребре

Пусть $\beta$ — двугранный угол при боковом ребре, например, при ребре $SB$. Этот угол образован двумя смежными боковыми гранями $(SAB)$ и $(SBC)$.

Для нахождения этого угла построим его линейный угол. Проведем в гранях $(SAB)$ и $(SBC)$ перпендикуляры к общему ребру $SB$.

В равностороннем треугольнике $\triangle SAB$ проведем высоту $AH$ к стороне $SB$. Длина этой высоты равна $AH = \frac{a\sqrt{3}}{2}$.

В равностороннем треугольнике $\triangle SBC$ проведем высоту $CH$ к стороне $SB$. Длина этой высоты равна $CH = \frac{a\sqrt{3}}{2}$.

Тогда $\angle AHC$ является линейным углом двугранного угла $\beta$. Рассмотрим треугольник $\triangle AHC$. Мы знаем длины его сторон: $AH = CH = \frac{a\sqrt{3}}{2}$. Третья сторона, $AC$, является диагональю квадрата $ABCD$, ее длина $AC = a\sqrt{2}$.

Применим к треугольнику $\triangle AHC$ теорему косинусов для нахождения угла $\beta = \angle AHC$:

$AC^2 = AH^2 + CH^2 - 2 \cdot AH \cdot CH \cdot \cos\beta$

$(a\sqrt{2})^2 = (\frac{a\sqrt{3}}{2})^2 + (\frac{a\sqrt{3}}{2})^2 - 2 \cdot \frac{a\sqrt{3}}{2} \cdot \frac{a\sqrt{3}}{2} \cdot \cos\beta$

$2a^2 = \frac{3a^2}{4} + \frac{3a^2}{4} - 2 \cdot \frac{3a^2}{4} \cdot \cos\beta$

$2a^2 = \frac{6a^2}{4} - \frac{6a^2}{4} \cdot \cos\beta$

$2a^2 = \frac{3a^2}{2} - \frac{3a^2}{2} \cdot \cos\beta$

Разделим обе части уравнения на $a^2$ (так как $a \neq 0$):

$2 = \frac{3}{2} - \frac{3}{2} \cos\beta$

$2 - \frac{3}{2} = - \frac{3}{2} \cos\beta$

$\frac{1}{2} = - \frac{3}{2} \cos\beta$

$\cos\beta = -\frac{1}{3}$.

Доказательство

Мы получили значения косинусов для обоих углов: $\cos \alpha = \frac{1}{\sqrt{3}}$ и $\cos\beta = -\frac{1}{3}$. Нам нужно доказать, что $\alpha = \frac{\beta}{2}$, что эквивалентно $\beta = 2\alpha$.

Воспользуемся формулой косинуса двойного угла: $\cos(2\alpha) = 2\cos^2\alpha - 1$.

Подставим найденное значение $\cos\alpha$:

$\cos(2\alpha) = 2 \cdot (\frac{1}{\sqrt{3}})^2 - 1 = 2 \cdot \frac{1}{3} - 1 = \frac{2}{3} - 1 = -\frac{1}{3}$.

Таким образом, мы получили, что $\cos(2\alpha) = -\frac{1}{3}$, и мы также знаем, что $\cos\beta = -\frac{1}{3}$. Следовательно, $\cos(2\alpha) = \cos\beta$.

Поскольку $\alpha$ — угол между плоскостью боковой грани и основанием, он острый ($0 < \alpha < 90^\circ$). Значит, $0 < 2\alpha < 180^\circ$. Угол $\beta$ — двугранный угол в пирамиде, он также находится в диапазоне $0 < \beta < 180^\circ$. Из равенства $\cos(2\alpha) = \cos\beta$ на этом интервале следует, что $2\alpha = \beta$.

Это доказывает, что двугранный угол между боковой гранью и основанием пирамиды ($\alpha$) вдвое меньше двугранного угла при боковом ребре ($\beta$).

Ответ: Утверждение доказано. Мы показали, что $\cos \alpha = \frac{1}{\sqrt{3}}$ и $\cos \beta = -\frac{1}{3}$, а из формулы двойного угла $\cos(2\alpha) = 2\cos^2\alpha - 1$ следует, что $\cos(2\alpha) = \cos\beta$, откуда $2\alpha = \beta$.

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