`cos 4x=cos 2x` को हल कीजिए |

Explanation

दिया है, `" " cos 4x = cos 2x`
`rArr " " cos 4x - cos 2x = 0`
`rArr -2 "sin"(4x+2x)/(2)"sin"(4x-2x)/(2)=0`
`rArr " " sin 3x sin x =0`
`rArr " " sin 3x = 0 " "` या `" " sin x =0`
`rArr " "3x=n pi " "` या `" " x=npi`
`rArr " " x =(n pi)/(3) " "` या `" " x = n pi`.