Question

Giúp mình câu 16 với ạ

Answer 1

Câu `16:`

`cos 5x-cos(x-\pi/3)=0`

`<=>cos 5x=cos(x-\pi/3)`

`<=>[(5x=x-\pi/3+k2\pi),(5x=-x+\pi/3+k2\pi):}`

`<=>[(x=-\pi/12+k\pi/2),(x=\pi/18+k\pi/3):}`

        `->\bb B`