Question

What are the exact solutions?

Answer 1

x = 2* pi* n

Explanation:

cos(2x) cos(x) + sin(2x) sin x =1

We know cos(s) cos(t) + sin(s) sin(t) = cos(s - t)

Using s =2x and t = x

cos (2x-x) =1

cos (x) =1

We know this occurs at 0, 2pi, 4 pi etc

x = 2* pi* n where n is an integer