Question

Упростить cosa-sina*ctga

Answer 1

$cos alpha -sin alpha *ctg alpha =cos alpha -sin alpha * frac{cos alpha }{sin alpha }= \ =cos alpha -cos alpha =0$

Answer 2

$cotalpha=frac{cosalpha}{sinalpha}\cosalpha-sinalpha*cotalpha=cosalpha-sinalpha*frac{cosalpha}{sinalpha}=cosalpha-cosalpha=0$