Question

$frac{sin alpha }{1 - cos alpha } - ctg alpha$
Помогите решить

Answer 1

$frac{sin alpha }{1 - cos alpha } - ctg alpha = frac{sin alpha }{1 - cos alpha } - frac{cosalpha}{sinalpha}= frac{sin^2 alpha -cosalpha(1-cosalpha)}{(1-cosalpha)sinalpha}=\ frac{sin^2 alpha -cosalpha+cos^2alpha}{(1-cosalpha)sinalpha}= frac{1-cosalpha}{(1-cosalpha)sinalpha}=frac{1}{sinalpha}$