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cos2x + tg^2x * cos2x-1= -tg^2 x
и
sin 4x- sin 5x - sin 6x+ sin 7x = -4 sin [tex] \frac{x}{2} [/tex] * sin x * sin [tex] \frac{11x}{2} [/tex]
cos2x + tg^2x * cos2x-1= -tg^2 x
и
sin 4x- sin 5x - sin 6x+ sin 7x = -4 sin [tex] \frac{x}{2} [/tex] * sin x * sin [tex] \frac{11x}{2} [/tex]
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Answers & Comments
cos2x+tg²x*cos2x-1= cos²x-sin²x+tg²x*(cos²x-sin²x)-cos²x-sin²x= -2sin²x+tg²x*cos²x-tg²x*sin²x=-2sin²x+sin²x-tgx(1-cos²x)= -sin²x-tg²x+sin²x= -tg²x
-tg²x=-tg²x
ч.т.д.