Question

Срочно нужна помощь по алгебре

Answer 1

$\displaystyle\bf\\2)\\\\\frac{Sin\Big(\dfrac{\pi }{2} +\alpha \Big)-Cos\Big(\pi +\alpha \Big)}{Sin\Big(2\pi -\alpha \Big)}= \frac{Cos\alpha -(-Cos\alpha )}{-Sin\alpha } =\\\\\\=-\frac{Cos\alpha +Cos\alpha }{Sin\alpha } =-\frac{2Cos\alpha }{Sin\alpha } =-2Ctg\alpha\\\\\\3)\\\\Cos30^\circ Cos15^\circ-Sin30^\circ Sin15^\circ=Cos\Big(30^\circ+15^\circ\Big)=\\\\\\=Cos45^\circ=\frac{\sqrt{2} }{2}$