Question

Упростить

cos(180+a)*cos(-a)$\frac{x}{y}$sin(-a)*sin(90+a)=

sin(П-a)*cos(2П-a)$\frac{x}{y}$tg(П-a)*cos(П-a)=

Answer 1

$\frac{cos(180+ \alpha )*cos(- \alpha )}{sin(- \alpha )*sin(90+ \alpha )} = \frac{-cos \alpha *cos \alpha }{-sin \alpha *cos \alpha } =ctg \alpha$

$\frac{sin( \pi - \alpha )*cos(2 \pi - \alpha )}{tg( \pi - \alpha )*cos( \pi - \alpha )} = \frac{sin \alpha *cos \alpha }{-tg \alpha *(-cos \alpha )} = \frac{sin \alpha }{tg \alpha } =cos \alpha$