Cos(-2x)+cos(1.5пи+2x)*tgx

Question

Cos(-2x)+cos(1.5пи+2x)*tgx

Answer 1

Cos(-2x)+cos(1,5π+2x)*tgx=cos2x+sin2x*tgx=cos2x+2sinxcosx*sinx/cosx=
=1-2sin²x+2sin²x=1