Question

ПОМОГИТЕ!! СРОЧНО НУЖНО
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Answer 1

$1)\; \; \frac{1-cosa}{1+cosa}\cdot tg^2(\frac{\pi}{2}-\frac{a}{2})-sin^2\frac{a}{3}=\frac{2sin^2\frac{a}{2}}{2cos^2\frac{a}{2}}\cdot ctg^2\frac{a}{2}-sin^2\frac{a}{3}=\\\\=tg^2\frac{a}{2}\cdot ctg^2\frac{a}{2}-sin^2\frac{a}{3}=1-sin^2\frac{a}{3}=cos^2\frac{a}{3}$

$2)\; \; \frac{sin(2a+\frac{3\pi }{2})}{sina-cosa}-cosa=\frac{-cos2a}{sina-cosa}-cosa=\frac{-cos2a\, \cdot \, (sina+cosa)}{-(cosa-sina)(sina+cosa)}-cosa=\\\\=\frac{cos2a(sina+cosa)}{cos^2a-sin^2a}-cosa=\frac{cos2a(sina+cosa)}{cos2a}-cosa=sina+cosa-cosa=sina$