use a double angle and half angle identity

Question

write Cos^2(x/2) - Sin(2x) in terms of Sin(x) and Cos(X) . ((hint use a double angle and half angle identity ))

Answer 1

Cos^2(x/2) = (1/2)(1+cos(x))

So, Cos^2(x/2) - Sin(2x) = (1/2)(1+cos(x)) - 2sin(x)cos(x)