Cos2x-3cos^2 2x=0 помогите решить

Question

Cos2x-3cos^2 2x=0 помогите решить

Answer 1

Cos2x=t
t-3t^2=0
t(1-3t)=0
t=0
1-3t=0
t=1/3
cos2x=0
x=-pi/4+pi/2k
cos2x=1/3
x=+-1/2arcos(1/3)+pin