Предмет: Математика, автор: poepaypal

Тупой вопрос, но все же.
Пусть дана произвольная трапеция ABCD.
С основаниями BC и AD.
Проведем диагональ AC, в силу параллельности BC и AD, угол BAC =ACD, но почему угол CAD не равен углу BCA? Прямые параллельны.

Ответы

Автор ответа: supportEU1

Почему это они не равны? Они же накрест лежащие

poepaypal: Я о том же, но к примеру вот эта задача : http://www.problems.ru/view_problem_details_new.php?id=55280

supportEU1: Ну? Там же на рисунке показано что они равны

poepaypal: Я перепутал, я про другую пару углов, я про углы BAC и ACD

supportEU1: Эти тоже равны. Показано на рисунке+у тебя по условию диагональ-биссектриса

s0807: про эти углы на рисунке ничего нет. вообще это не накрест лежащие, если продлить параллельные прямые во все стороны, то будет видно

supportEU1: Вообще-то углы про которые он вначале спросил, накрест лежащие

s0807: это да) получается одна пара углов, которые образует диагональ накрест лежащие, а вторая нет

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