ctg^2α(1-cos2α)+cos^2α= помогите=)

Question

ctg^2α(1-cos2α)+cos^2α=

помогите=)

Answer 1

sin^2a/cos^2a * (1-1+2sin^2a) + cos^2a = cos^2a *2sin^2a / sin^2a +cos^2a = 3cos^2a