Giải phương trình \(1 + \sin x + \cos 3x = \cos x...

Câu hỏi: Giải phương trình \(1 + \sin x + \cos 3x = \cos x + \sin 2x + \cos 2x\).

A \(x = k\pi \), \(x = \dfrac{\pi }{6} + \dfrac{{k\pi }}{3}\), \(x = \dfrac{\pi }{{12}} + k\pi \), \(x = \dfrac{{5\pi }}{{7}} + k\pi \).

B \(x = k2\pi \), \(x = \dfrac{\pi }{3} + \dfrac{{k2\pi }}{3}\), \(x = \dfrac{\pi }{{12}} + k\pi \), \(x = \dfrac{{5\pi }}{{12}} + k\pi \).

C \(x = k\pi \), \(x = \dfrac{\pi }{3} + \dfrac{{k2\pi }}{3}\), \(x = \dfrac{\pi }{{12}} + k\pi \), \(x = \dfrac{{5\pi }}{{12}} + k\pi \).

D \(x = k2\pi \), \(x = \dfrac{\pi }{6} + \dfrac{{k2\pi }}{3}\), \(x = \dfrac{\pi }{{12}} + k\pi \), \(x = \dfrac{{7\pi }}{{12}} + k\pi \).