Express 1 - 2*cos(2a) as a product

Answer 1

One way:
1 - 2*cos(2x)
= sin^2 x + cos^2 x - 2(cos^2 x - sin^2 x)
= 3sin^2 x - cos^2 x
= (√3sinx + cosx)(√3sinx - cosx)

oops, replace all x's with a's, makes no difference