Cos7x cosx+sin7x sinx=0.5

Question

Cos7x cosx+sin7x sinx=0.5

Answer 1

Cos 6x = 1/2
6x = +- arcCos 1/2 + 2π k, k∈Z
6x = +-π/3 + 2πk, k∈Z
x = +- π/18 + πK/3, k ∈Z