Предмет: Алгебра, автор: гриолип

Докажите тождество
А) sin 2альфа=(sinальфа+cosальфа)^2 -1

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Автор ответа: Аноним

0

(sina+cosa)^2-1= (sina)^2+2*sina*cosa+(cosa)^2-((sina)^2+(cosa)^2)= (sina)^2+2*sina*cosa+(cosa)^2-(sina)^2-(cosa)^2)=2*sina*cosa=sin2a

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