Предмет: Геометрия, автор: Kretov02

в треугольнике ABC, угол С=90, AC=4 корня из 91, AB= 40 найти cosB

Ответы

Автор ответа: UglyRat

1

Найдем сторону СВ по теореме Пифагора:
ВС²=40²-(4√91)²
ВС²=1600-1456
ВС²=144
ВС=12
cos∠В= $\frac{12}{40} = \frac{6}{20} = \frac{3}{10} =0.3$

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