Предмет: Алгебра, автор: zarnas

sin=7/25 0<альфа<п/2 найти cos2альфа?

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Автор ответа: IZUBR

0

Все и тут просто:)

Применяешь формулу основного тригонометрического тождества, находишь косинус, а там зная формулу косинуса двойного угла, и его. Особое внимаение уделяй периоду, но в данном задании он не играет большой роли.

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