Question

Упростите: (1-cos2$alpha$)/(1+$tg^{2}$$alpha$)

Answer 1

$frac{1+cos2a}{1+tg^2a}=frac{1+2cos^2a-1}{1+frac{sin^2a}{cos^2a}} =\ frac{2cos^2a}{frac{1}{cos^2a}}=2cos^4a$