Question

Cos^2x -sin ^2x- 2cos^ 2 2x =0

Answer 1

cos2x-cos^2x=0
2cos^2 x-1-cos^x=0
3cos^2 x=1
cos^2 x=1/3
cosx=+-√3/3
x=+-arccos√3/3+2πk,k∈Z
x=+-(π-arccos√3/3)+2πk,k∈Z