Question

Cos^3x . Cos2x - cos^2x=0

Answer 1

`cos^3 x.cos 2x-cos^2 x=0`

`<=>cos^2 x(cos x.cos 2x-1)=0`

`<=>cos x[cos x(2cos^2 x-1)-1]=0`

`<=>cos x(2cos^3 x-cos x-1)=0`

`<=>[(cos x=0),(cos x=1):}`

`<=>[(x=\pi/2+k\pi),(x=k2\pi):}`       `(k in ZZ)`

Answer 2

Đề là:\(cos^3x . cos2x - cos^2x = 0\) à bạn?