Question

cos(180 ̊+a)cos(-a)/(sin(-a)sin(90 ̊+a)) упростить

 

Answer 1

$frac{cos(180+alpha)cos(-alpha)}{sin(-alpha)sin(90+alpha)}=frac{-cosalpha cdot cosalpha}{-sinalpha cdot cosalpha}=frac{cosalpha}{sinalpha}=ctgalpha$