Задание:
(sin^2 (173) -cos^2 (187) /sin76
Решение:
(sin^2 (173) -cos^2 (187) /sin76=(sin^2 (180-7) -cos^2 (180+7) /sin76=(sin^2 (7) -cos^2 (7) /sin (90-14)=- (cos^2 (7) -sin^2 (7) /cos (14)=-cos (2*7) /cos (14)=-cos (14) /cos (14)=-1
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