Question

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Answer 1

Ответ:

а)$sin(\frac{3\pi }{3} -\alpha )=sin(\pi +\frac{\pi }{2} -\alpha )=-sin(\frac{\pi }{2} -\alpha )=-cos\alpha$

$tg(\frac{\pi }{2} +\alpha )=-ctg\alpha$

$-cos\alpha *(-ctg\alpha )=cos\alpha *\frac{cos\alpha }{sin\alpha } =\frac{cos^{2}\alpha }{sin\alpha }$

б)$cos^{2} (\alpha -\frac{3\pi }{2} )=cos^{2} (\frac{3\pi }{2}-\alpha)=cos^{2} (\pi +\frac{\pi }{2} -\alpha )=cos^{2} (\frac{\pi }{2} -\alpha )=sin^{2} \alpha$

$sin^{2}(-\alpha )=(-sin\alpha )^{2} =sin^{2} \alpha$

$sin^{2} \alpha +sin^{2} \alpha=2*sin^{2} \alpha$