Giải phương trình \({\sin ^2}x = \sin 3x + \cos x\...

Câu hỏi: Giải phương trình \({\sin ^2}x = \sin 3x + \cos x\left( {\cos x - 1} \right)\)

A \(x = \frac{\pi }{4} + k\pi;\,\,x =  - \frac{\pi }{2} + k2\pi ;\,\,x = \frac{{2k\pi }}{3}\,\,\left( {k \in Z} \right)\)

B \(x = \frac{\pi }{4} + k\pi ;\,\,x = \frac{\pi }{2} + k\pi ;\,\,x = \frac{{2k\pi }}{3}\,\,\left( {k \in Z} \right)\)

C \(x = \frac{\pi }{3} + k\pi ;\,\,x =  - \frac{\pi }{2} + k2\pi ;\,\,x =  - \frac{{2k\pi }}{3}\,\,\left( {k \in Z} \right)\)

D \(x = \frac{\pi }{6} + k\pi ;\,\,x =  - \frac{\pi }{2} + k\pi ;\,\,x = \frac{{2k\pi }}{3}\,\,\left( {k \in Z} \right)\)