Предмет: Геометрия, автор: marlen2407

четырехугольнике ABCD BC=15см, CD=9см, AD=13см, BD=12см, Найдите AB.

Ответы

Автор ответа: ymnik6557

0

В треугольнике ВСD отношение сторон CD:BD:BC=3:4:5, что указывает на то, что этот треугольник прямоугольный ( египетский). То, что косинус угла ВDС=0, и этот угол равен 90°, можно найти и по т.косинусов (проверьте). Тогда из равенства ∠АВD=∠CDB треугольник АВС – прямоугольный. По т.Пифагора найдем АВ=√(13²-12²)=5 см.

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