Solve: `cos4x=cos2x`

Explanation

Given equation: `cos4x=cos2x`
`rArr 4x=(2npi+-2x)`
then, taking `+` sign `4x = 2npi+2x`
or `4x-2x=2npi`
`rArr x=npi, n in Z`
or `4x+2x=2npi`
or `6x=2npi rArr x=(npi)/(3), n in Z`
Therefore, general solution of given equation is `x=npi`.
or `x=(npi)/(3), n in Z` Ans.