Номер 228, страница 71 - 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 1. Понятие многогранника. Призма - номер 228, страница 71.

App\Models\Task {#1030 // resources/views/models/task/default.blade.php
  #connection: "mysql"
  #table: "tasks"
  #primaryKey: "id"
  #keyType: "int"
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  #attributes: array:24 [
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    "created_at" => "2026-04-10 13:58:26"
    "updated_at" => null
    "field_page_start" => "71"
    "field_page_end" => null
    "field_url" => "/10-klass/geometrija/atanasjan-uchebnik/00-228"
    "field_display_title" => "228"
    "field_outside_task" => null
    "field_task_type" => Illuminate\Database\Eloquent\Collection {#1037
      #items: array:1 [
        0 => App\Models\Term {#1036
          #connection: "mysql"
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          #attributes: array:6 [
            "id" => 26
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "name" => "номер"
            "field_cases" => array:6 [
              "field_accusative_case" => "номер"
              "field_creative_case" => "номером"
              "field_dative_case" => "номеру"
              "field_genitive_case" => "номера"
              "field_nominative_case" => "номер"
              "field_prepositional_case" => "номере"
            ]
            "field_short_name" => ""
          ]
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            "name" => "номер"
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              "field_accusative_case" => "номер"
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              "field_prepositional_case" => "номере"
            ]
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            "field_url" => null
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                0 => App\Models\Book {#1049
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                            "id" => 6477
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
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                            "field_abbreviated_name" => null
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                            "updated_at" => null
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                            "field_abbreviated_name" => null
                            "field_cases" => array:6 [ …6]
                            "field_foreign_lang_name" => null
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                            "field_subject_type" => "technical_subject"
                            "field_translit" => "geometrija"
                          ]
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                    "field_class" => Illuminate\Database\Eloquent\Collection {#1052
                      #items: array:2 [
                        0 => App\Models\Term {#1053
                          #connection: "mysql"
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                          #attributes: array:6 [
                            "id" => 5459
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "10"
                            "field_cases" => array:6 [ …6]
                            "field_translit" => "desjatyj"
                          ]
                          #original: array:6 [
                            "id" => 5459
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                             …3
                          ]
                          #changes: []
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                          #guarded: array:1 [ …1]
                        }
                        1 => App\Models\Term {#1054
                          #connection: "mysql"
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                          #keyType: "int"
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                          #attributes: array:6 [ …6]
                          #original: array:6 [ …6]
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                          +timestamps: true
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                          #visible: []
                          #fillable: []
                          #guarded: array:1 [ …1]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1055
                      #items: array:1 [
                        0 => App\Models\Term {#1056
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
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                          #attributes: array:6 [ …6]
                          #original: array:6 [ …6]
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                          #guarded: array:1 [ …1]
                        }
                      ]
                      #escapeWhenCastingToString: false
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                    "field_author" => Illuminate\Database\Eloquent\Collection {#1057
                      #items: array:5 [
                        0 => App\Models\Term {#1058
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
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                          #original: array:12 [ …12]
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                        }
                        1 => App\Models\Term {#1059
                          #connection: "mysql"
                          #table: "terms"
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                        }
                        2 => App\Models\Term {#1060
                          #connection: "mysql"
                          #table: "terms"
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                        }
                        3 => App\Models\Term {#1061
                          #connection: "mysql"
                          #table: "terms"
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                        }
                        4 => App\Models\Term {#1062
                          #connection: "mysql"
                          #table: "terms"
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                    "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1063
                      #items: []
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                    "field_book_type" => Illuminate\Database\Eloquent\Collection {#1064
                      #items: array:1 [
                        0 => App\Models\Term {#1065
                          #connection: "mysql"
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                    "field_country" => Illuminate\Database\Eloquent\Collection {#1066
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                        0 => App\Models\Term {#1067
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                          #attributes: array:10 [ …10]
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                        }
                      ]
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                    }
                    "field_publication_number" => "11"
                    "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1076
                      #items: array:1 [
                        0 => App\Models\Term {#1077
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
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                          #perPage: 15
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                          #attributes: array:6 [ …6]
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                          #touches: []
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                          #visible: []
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                          #guarded: array:1 [ …1]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1078
                      #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 {#1079
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_new_book" => Illuminate\Database\Eloquent\Collection {#1080
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                      #escapeWhenCastingToString: false
                    }
                    "field_old_book" => Illuminate\Database\Eloquent\Collection {#1081
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_url" => "/10-klass/geometrija/atanasjan-uchebnik"
                    "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1082
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                        0 => App\Models\Term {#1083
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
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                          #attributes: array:6 [ …6]
                          #original: array:6 [ …6]
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                          #dateFormat: null
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                          #touches: []
                          +timestamps: true
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                          #hidden: []
                          #visible: []
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                          #guarded: array:1 [ …1]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_metatags_title" => null
                    "field_metatags_description" => null
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                    "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 {#1051}
                    "field_class" => Illuminate\Database\Eloquent\Collection {#1052}
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1055}
                    "field_author" => Illuminate\Database\Eloquent\Collection {#1057}
                    "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1063}
                    "field_book_type" => Illuminate\Database\Eloquent\Collection {#1064}
                    "field_country" => Illuminate\Database\Eloquent\Collection {#1066}
                    "field_city" => Illuminate\Database\Eloquent\Collection {#1068}
                    "field_series" => Illuminate\Database\Eloquent\Collection {#1070}
                    "field_umk" => Illuminate\Database\Eloquent\Collection {#1071}
                    "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1072}
                    "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1074}
                    "field_publication_number" => "11"
                    "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1076}
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                    "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"
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                    "field_default_folder" => "/geometrija_10/atanasjan-u23/"
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                    "field_cover" => array:1 [
                      0 => "/media/geometrija_10/atanasjan-u23/covers/cover1.webp?ts=1739363242"
                    ]
                    "field_cover_alts" => array:1 [
                      0 => ""
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                      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 {#1079}
                    "field_new_book" => Illuminate\Database\Eloquent\Collection {#1080}
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                    "field_url" => "/10-klass/geometrija/atanasjan-uchebnik"
                    "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1082}
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                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1084
              #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 {#1050}
            "field_page_start" => "63"
            "field_branch_display" => "0"
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            "field_display_branch_page" => "1"
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            "field_h1" => null
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            "field_branch_cover" => []
            "field_branch_covers" => []
            "book" => Illuminate\Database\Eloquent\Collection {#1086}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1084}
          ]
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            0 => "*"
          ]
        }
      ]
      #escapeWhenCastingToString: false
    }
    "parent_branches" => Illuminate\Database\Eloquent\Collection {#1121
      #items: array:2 [
        0 => App\Models\Branch {#1129
          #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" => 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 {#1130
              #items: array:1 [
                0 => App\Models\Term {#1047}
              ]
              #escapeWhenCastingToString: false
            }
            "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 {#1131
              #items: array:1 [
                0 => App\Models\Book {#1049}
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1132
              #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
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            "field_page_start" => "63"
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            "field_branch_cover" => []
            "field_branch_covers" => []
            "book" => Illuminate\Database\Eloquent\Collection {#1131}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1132}
          ]
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          #touches: []
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            0 => "*"
          ]
        }
        1 => App\Models\Branch {#1133
          #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" => 744381
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Понятие многогранника. Призма"
            "field_branch_order" => "1"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1137
              #items: array:1 [
                0 => App\Models\Term {#1134
                  #connection: "mysql"
                  #table: "terms"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
                  #withCount: []
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                  #perPage: 15
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                  #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: []
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                  #attributeCastCache: []
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                  #guarded: array:1 [
                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "field_page_start" => "63"
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            "field_navigation_title" => null
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            "field_h1" => null
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            "book" => Illuminate\Database\Eloquent\Collection {#1136
              #items: array:1 [
                0 => App\Models\Book {#1049}
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1135
              #items: array:1 [
                0 => App\Models\Branch {#1045}
              ]
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 744381
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            "field_page_start" => "63"
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            "book" => Illuminate\Database\Eloquent\Collection {#1136}
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          ]
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            0 => "*"
          ]
        }
      ]
      #escapeWhenCastingToString: false
    }
    "content" => Illuminate\Database\Eloquent\Collection {#1038
      #items: array:6 [
        0 => App\Models\Element {#1109
          #connection: "mysql"
          #table: "elements"
          #primaryKey: "id"
          #keyType: "int"
          +incrementing: true
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          #attributes: array:7 [
            "id" => 938877
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1098
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                0 => App\Models\Edition {#1106
                  #connection: "mysql"
                  #table: "editions"
                  #primaryKey: "id"
                  #keyType: "int"
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                  #attributes: array:21 [
                    "id" => 2315
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "title" => "Условие"
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                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1105 …2}
                    "field_content_type" => "free"
                    "field_content_mode" => "text, image"
                    "field_page_content_mode" => "image"
                    "field_content_text_checked" => null
                    "field_page_content_text_checked" => "0"
                    "field_solution_author" => "Автор"
                    "field_moderator" => "pasha"
                    "field_edition_type" => "statement"
                    "field_root_dir" => "0-"
                    "field_responsible" => Illuminate\Database\Eloquent\Collection {#1104 …2}
                    "field_comment" => null
                    "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1102 …2}
                    "field_process_formula" => "wiris"
                    "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1103 …2}
                    "field_content_source" => null
                  ]
                  #original: array:21 [
                    "id" => 2315
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "title" => "Условие"
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                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1105 …2}
                    "field_content_type" => "free"
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                    "field_page_content_text_checked" => "0"
                    "field_solution_author" => "Автор"
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                    "field_root_dir" => "0-"
                    "field_responsible" => Illuminate\Database\Eloquent\Collection {#1104 …2}
                    "field_comment" => null
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                    "field_content_source" => null
                  ]
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                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "task" => array:2 [
              "refs" => "744643"
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            "text" => "<p> <b>228.</b> Основанием наклонной призмы ABCА₁В₁С₁ является равнобедренный треугольник ABC, в котором <span class="long">АС = AB = 13 см,</span> <span class="long">ВС = 10 см,</span> а боковое ребро призмы образует с плоскостью основания угол в 45°. Проекцией вершины А₁ является точка пересечения медиан треугольника ABC. Найдите площадь грани СС₁В₁В. </p>"
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            "text" => "<p> <b>228.</b> Основанием наклонной призмы ABCА₁В₁С₁ является равнобедренный треугольник ABC, в котором <span class="long">АС = AB = 13 см,</span> <span class="long">ВС = 10 см,</span> а боковое ребро призмы образует с плоскостью основания угол в 45°. Проекцией вершины А₁ является точка пересечения медиан треугольника ABC. Найдите площадь грани СС₁В₁В. </p>"
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        2 => App\Models\Element {#1100
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        3 => App\Models\Element {#1094
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        4 => App\Models\Element {#1043
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        5 => App\Models\Element {#1143
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            "text" => "<p>По условию задачи мы имеем наклонную призму $ABCA_1B_1C_1$, в основании которой лежит равнобедренный треугольник $ABC$. Дано:</p><ul><li>Основание $ABC$ – равнобедренный треугольник.</li> <li>Боковые стороны $AC = AB = 13$ см.</li> <li>Основание треугольника $BC = 10$ см.</li> <li>Угол между боковым ребром (например, $AA_1$) и плоскостью основания $(ABC)$ равен $45^\circ$.</li> <li>Проекция вершины $A_1$ на плоскость основания $(ABC)$ — это точка $O$, которая является точкой пересечения медиан (центроидом) треугольника $ABC$.</li></ul><p>Нужно найти площадь боковой грани $CC_1B_1B$. Эта грань является параллелограммом.</p><p><strong>1. Найдем длину медианы $AM$ треугольника $ABC$.</strong></p><p>Проведем в треугольнике $ABC$ медиану $AM$ к основанию $BC$. Так как треугольник $ABC$ равнобедренный с основанием $BC$, медиана $AM$ также является высотой и биссектрисой. Следовательно, $AM \perp BC$ и точка $M$ — середина $BC$. $BM = MC = \frac{BC}{2} = \frac{10}{2} = 5$ см. Рассмотрим прямоугольный треугольник $\triangle AMC$. По теореме Пифагора: $AC^2 = AM^2 + MC^2$ $13^2 = AM^2 + 5^2$ $169 = AM^2 + 25$ $AM^2 = 169 - 25 = 144$ $AM = \sqrt{144} = 12$ см.</p><p><strong>2. Найдем расстояние $AO$ и высоту призмы $H$.</strong></p><p>Точка $O$ — точка пересечения медиан треугольника $ABC$. Медианы делятся точкой пересечения в отношении 2:1, считая от вершины. Точка $O$ лежит на медиане $AM$. $AO = \frac{2}{3} AM = \frac{2}{3} \cdot 12 = 8$ см.</p><p>По условию, $O$ является проекцией $A_1$ на плоскость $(ABC)$. Это значит, что $A_1O$ — высота призмы $H$, и $A_1O \perp (ABC)$. Отрезок $AO$ является проекцией наклонной $AA_1$ (бокового ребра) на плоскость основания. Угол между боковым ребром и плоскостью основания — это угол $\angle A_1AO$. По условию, $\angle A_1AO = 45^\circ$.</p><p>Рассмотрим прямоугольный треугольник $\triangle A_1AO$ (прямой угол $\angle A_1OA$). Так как один из острых углов равен $45^\circ$, то этот треугольник равнобедренный, и $A_1O = AO$. Высота призмы $H = A_1O = AO = 8$ см.</p><p><strong>3. Найдем длину бокового ребра $L$.</strong></p><p>Длина бокового ребра $L = AA_1$. В том же прямоугольном треугольнике $\triangle A_1AO$: $AA_1 = \frac{AO}{\cos(45^\circ)} = \frac{8}{\frac{\sqrt{2}}{2}} = \frac{16}{\sqrt{2}} = 8\sqrt{2}$ см. Все боковые ребра призмы равны, следовательно, $CC_1 = BB_1 = AA_1 = 8\sqrt{2}$ см.</p><p><strong>4. Найдем площадь грани $CC_1B_1B$.</strong></p><p>Грань $CC_1B_1B$ является параллелограммом со сторонами $BC$ и $CC_1$. Площадь параллелограмма можно найти по формуле $S = a \cdot b \cdot \sin\alpha$, где $a$ и $b$ — смежные стороны, а $\alpha$ — угол между ними. В нашем случае $S = BC \cdot CC_1 \cdot \sin(\angle C_1CB)$.</p><p>Найдем угол $\angle C_1CB$. Так как $AM$ — высота в $\triangle ABC$, то $AM \perp BC$. Прямая $AO$ лежит на прямой $AM$, следовательно, $AO \perp BC$. $AO$ — это проекция наклонной $AA_1$ на плоскость $(ABC)$. По теореме о трех перпендикулярах: если проекция наклонной ($AO$) перпендикулярна некоторой прямой в плоскости ($BC$), то и сама наклонная ($AA_1$) перпендикулярна этой прямой. Следовательно, $AA_1 \perp BC$.</p><p>Боковые ребра призмы параллельны, поэтому $CC_1 \parallel AA_1$. Если $AA_1 \perp BC$, то и $CC_1 \perp BC$. Это означает, что угол между ребром $CC_1$ и ребром $BC$ равен $90^\circ$. Таким образом, параллелограмм $CC_1B_1B$ на самом деле является прямоугольником.</p><p>Площадь прямоугольника $CC_1B_1B$ равна произведению его смежных сторон: $S_{CC_1B_1B} = BC \cdot CC_1$ $S_{CC_1B_1B} = 10 \cdot 8\sqrt{2} = 80\sqrt{2}$ см$^2$.</p><p><b>Ответ:</b> $80\sqrt{2}$ см$^2$.</p>"
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            "text" => "<p>По условию задачи мы имеем наклонную призму $ABCA_1B_1C_1$, в основании которой лежит равнобедренный треугольник $ABC$. Дано:</p><ul><li>Основание $ABC$ – равнобедренный треугольник.</li> <li>Боковые стороны $AC = AB = 13$ см.</li> <li>Основание треугольника $BC = 10$ см.</li> <li>Угол между боковым ребром (например, $AA_1$) и плоскостью основания $(ABC)$ равен $45^\circ$.</li> <li>Проекция вершины $A_1$ на плоскость основания $(ABC)$ — это точка $O$, которая является точкой пересечения медиан (центроидом) треугольника $ABC$.</li></ul><p>Нужно найти площадь боковой грани $CC_1B_1B$. Эта грань является параллелограммом.</p><p><strong>1. Найдем длину медианы $AM$ треугольника $ABC$.</strong></p><p>Проведем в треугольнике $ABC$ медиану $AM$ к основанию $BC$. Так как треугольник $ABC$ равнобедренный с основанием $BC$, медиана $AM$ также является высотой и биссектрисой. Следовательно, $AM \perp BC$ и точка $M$ — середина $BC$. $BM = MC = \frac{BC}{2} = \frac{10}{2} = 5$ см. Рассмотрим прямоугольный треугольник $\triangle AMC$. По теореме Пифагора: $AC^2 = AM^2 + MC^2$ $13^2 = AM^2 + 5^2$ $169 = AM^2 + 25$ $AM^2 = 169 - 25 = 144$ $AM = \sqrt{144} = 12$ см.</p><p><strong>2. Найдем расстояние $AO$ и высоту призмы $H$.</strong></p><p>Точка $O$ — точка пересечения медиан треугольника $ABC$. Медианы делятся точкой пересечения в отношении 2:1, считая от вершины. Точка $O$ лежит на медиане $AM$. $AO = \frac{2}{3} AM = \frac{2}{3} \cdot 12 = 8$ см.</p><p>По условию, $O$ является проекцией $A_1$ на плоскость $(ABC)$. Это значит, что $A_1O$ — высота призмы $H$, и $A_1O \perp (ABC)$. Отрезок $AO$ является проекцией наклонной $AA_1$ (бокового ребра) на плоскость основания. Угол между боковым ребром и плоскостью основания — это угол $\angle A_1AO$. По условию, $\angle A_1AO = 45^\circ$.</p><p>Рассмотрим прямоугольный треугольник $\triangle A_1AO$ (прямой угол $\angle A_1OA$). Так как один из острых углов равен $45^\circ$, то этот треугольник равнобедренный, и $A_1O = AO$. Высота призмы $H = A_1O = AO = 8$ см.</p><p><strong>3. Найдем длину бокового ребра $L$.</strong></p><p>Длина бокового ребра $L = AA_1$. В том же прямоугольном треугольнике $\triangle A_1AO$: $AA_1 = \frac{AO}{\cos(45^\circ)} = \frac{8}{\frac{\sqrt{2}}{2}} = \frac{16}{\sqrt{2}} = 8\sqrt{2}$ см. Все боковые ребра призмы равны, следовательно, $CC_1 = BB_1 = AA_1 = 8\sqrt{2}$ см.</p><p><strong>4. Найдем площадь грани $CC_1B_1B$.</strong></p><p>Грань $CC_1B_1B$ является параллелограммом со сторонами $BC$ и $CC_1$. Площадь параллелограмма можно найти по формуле $S = a \cdot b \cdot \sin\alpha$, где $a$ и $b$ — смежные стороны, а $\alpha$ — угол между ними. В нашем случае $S = BC \cdot CC_1 \cdot \sin(\angle C_1CB)$.</p><p>Найдем угол $\angle C_1CB$. Так как $AM$ — высота в $\triangle ABC$, то $AM \perp BC$. Прямая $AO$ лежит на прямой $AM$, следовательно, $AO \perp BC$. $AO$ — это проекция наклонной $AA_1$ на плоскость $(ABC)$. По теореме о трех перпендикулярах: если проекция наклонной ($AO$) перпендикулярна некоторой прямой в плоскости ($BC$), то и сама наклонная ($AA_1$) перпендикулярна этой прямой. Следовательно, $AA_1 \perp BC$.</p><p>Боковые ребра призмы параллельны, поэтому $CC_1 \parallel AA_1$. Если $AA_1 \perp BC$, то и $CC_1 \perp BC$. Это означает, что угол между ребром $CC_1$ и ребром $BC$ равен $90^\circ$. Таким образом, параллелограмм $CC_1B_1B$ на самом деле является прямоугольником.</p><p>Площадь прямоугольника $CC_1B_1B$ равна произведению его смежных сторон: $S_{CC_1B_1B} = BC \cdot CC_1$ $S_{CC_1B_1B} = 10 \cdot 8\sqrt{2} = 80\sqrt{2}$ см$^2$.</p><p><b>Ответ:</b> $80\sqrt{2}$ см$^2$.</p>"
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№228 (с. 71)
Условие. №228 (с. 71)
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 71, номер 228, Условие

228. Основанием наклонной призмы ABCА₁В₁С₁ является равнобедренный треугольник ABC, в котором АС = AB = 13 см, ВС = 10 см, а боковое ребро призмы образует с плоскостью основания угол в 45°. Проекцией вершины А₁ является точка пересечения медиан треугольника ABC. Найдите площадь грани СС₁В₁В.

Решение 2. №228 (с. 71)
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 71, номер 228, Решение 2
Решение 3. №228 (с. 71)
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 71, номер 228, Решение 3
Решение 4. №228 (с. 71)
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 71, номер 228, Решение 4
Решение 5. №228 (с. 71)
Решение 6. №228 (с. 71)

По условию задачи мы имеем наклонную призму $ABCA_1B_1C_1$, в основании которой лежит равнобедренный треугольник $ABC$. Дано:

  • Основание $ABC$ – равнобедренный треугольник.
  • Боковые стороны $AC = AB = 13$ см.
  • Основание треугольника $BC = 10$ см.
  • Угол между боковым ребром (например, $AA_1$) и плоскостью основания $(ABC)$ равен $45^\circ$.
  • Проекция вершины $A_1$ на плоскость основания $(ABC)$ — это точка $O$, которая является точкой пересечения медиан (центроидом) треугольника $ABC$.

Нужно найти площадь боковой грани $CC_1B_1B$. Эта грань является параллелограммом.

1. Найдем длину медианы $AM$ треугольника $ABC$.

Проведем в треугольнике $ABC$ медиану $AM$ к основанию $BC$. Так как треугольник $ABC$ равнобедренный с основанием $BC$, медиана $AM$ также является высотой и биссектрисой. Следовательно, $AM \perp BC$ и точка $M$ — середина $BC$. $BM = MC = \frac{BC}{2} = \frac{10}{2} = 5$ см. Рассмотрим прямоугольный треугольник $\triangle AMC$. По теореме Пифагора: $AC^2 = AM^2 + MC^2$ $13^2 = AM^2 + 5^2$ $169 = AM^2 + 25$ $AM^2 = 169 - 25 = 144$ $AM = \sqrt{144} = 12$ см.

2. Найдем расстояние $AO$ и высоту призмы $H$.

Точка $O$ — точка пересечения медиан треугольника $ABC$. Медианы делятся точкой пересечения в отношении 2:1, считая от вершины. Точка $O$ лежит на медиане $AM$. $AO = \frac{2}{3} AM = \frac{2}{3} \cdot 12 = 8$ см.

По условию, $O$ является проекцией $A_1$ на плоскость $(ABC)$. Это значит, что $A_1O$ — высота призмы $H$, и $A_1O \perp (ABC)$. Отрезок $AO$ является проекцией наклонной $AA_1$ (бокового ребра) на плоскость основания. Угол между боковым ребром и плоскостью основания — это угол $\angle A_1AO$. По условию, $\angle A_1AO = 45^\circ$.

Рассмотрим прямоугольный треугольник $\triangle A_1AO$ (прямой угол $\angle A_1OA$). Так как один из острых углов равен $45^\circ$, то этот треугольник равнобедренный, и $A_1O = AO$. Высота призмы $H = A_1O = AO = 8$ см.

3. Найдем длину бокового ребра $L$.

Длина бокового ребра $L = AA_1$. В том же прямоугольном треугольнике $\triangle A_1AO$: $AA_1 = \frac{AO}{\cos(45^\circ)} = \frac{8}{\frac{\sqrt{2}}{2}} = \frac{16}{\sqrt{2}} = 8\sqrt{2}$ см. Все боковые ребра призмы равны, следовательно, $CC_1 = BB_1 = AA_1 = 8\sqrt{2}$ см.

4. Найдем площадь грани $CC_1B_1B$.

Грань $CC_1B_1B$ является параллелограммом со сторонами $BC$ и $CC_1$. Площадь параллелограмма можно найти по формуле $S = a \cdot b \cdot \sin\alpha$, где $a$ и $b$ — смежные стороны, а $\alpha$ — угол между ними. В нашем случае $S = BC \cdot CC_1 \cdot \sin(\angle C_1CB)$.

Найдем угол $\angle C_1CB$. Так как $AM$ — высота в $\triangle ABC$, то $AM \perp BC$. Прямая $AO$ лежит на прямой $AM$, следовательно, $AO \perp BC$. $AO$ — это проекция наклонной $AA_1$ на плоскость $(ABC)$. По теореме о трех перпендикулярах: если проекция наклонной ($AO$) перпендикулярна некоторой прямой в плоскости ($BC$), то и сама наклонная ($AA_1$) перпендикулярна этой прямой. Следовательно, $AA_1 \perp BC$.

Боковые ребра призмы параллельны, поэтому $CC_1 \parallel AA_1$. Если $AA_1 \perp BC$, то и $CC_1 \perp BC$. Это означает, что угол между ребром $CC_1$ и ребром $BC$ равен $90^\circ$. Таким образом, параллелограмм $CC_1B_1B$ на самом деле является прямоугольником.

Площадь прямоугольника $CC_1B_1B$ равна произведению его смежных сторон: $S_{CC_1B_1B} = BC \cdot CC_1$ $S_{CC_1B_1B} = 10 \cdot 8\sqrt{2} = 80\sqrt{2}$ см$^2$.

Ответ: $80\sqrt{2}$ см$^2$.

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