Question

ctg^2 alpha -cos^2 alpha -ctg^2 alpha *cos^2 alpha [/tex]

Answer 1

$ctg^2 alpha -cos^2 alpha -ctg^2 alpha cos^2 alpha =(ctg^2 alpha -ctg^2 alpha cos^2 alpha )-cos^2 alpha =\=ctg^2 alpha (1-cos^2 alpha )-cos^2 alpha =ctg^2 alpha sin^2 alpha -cos^2 alpha = frac{cos^2 alpha }{sin^2 alpha } sin^2 alpha-\-cos^2 alpha=cos^2 alpha -cos^2 alpha =0$