Phương trình

Câu hỏi: Phương trình $\sin 2x=\cos x$ có nghiệm là

A. $\left[\begin{array}{l}x=\frac{\pi }{6}+\frac{k\pi }{3}\\ x=\frac{\pi }{2}+k2\pi \end{array}\right.\left(k\in Z\right)$

B. $\left[\begin{array}{l}x=\frac{\pi }{6}+\frac{k\pi }{3}\\ x=\frac{\pi }{3}+k2\pi \end{array}\right.\left(k\in Z\right)$

C. $\left[\begin{array}{l}x=\frac{\pi }{6}+k2\pi \\ x=\frac{\pi }{2}+k2\pi \end{array}\right.\left(k\in Z\right)$

D. $\left[\begin{array}{l}x=\frac{\pi }{6}+\frac{k2\pi }{3}\\ x=\frac{\pi }{2}+k2\pi \end{array}\right.\left(k\in Z\right)$