Phương trình 

Câu hỏi: Phương trình $\sqrt{3}\cos 3x+\sin 3x=\sqrt{2}$ có nghiệm là:

A. $\left[\begin{array}{l}x=-\frac{\pi }{36}+\frac{k2\pi }{3}\\ x=\frac{5\pi }{36}+\frac{k2\pi }{3}\end{array}\right.(k\in Z)$

B. $\left[\begin{array}{l}x=-\frac{\pi }{36}+\frac{k\pi }{3}\\ x=\frac{5\pi }{36}+\frac{k\pi }{3}\end{array}\right.(k\in Z)$

C. $\left[\begin{array}{l}x=\frac{\pi }{36}+\frac{k2\pi }{3}\\ x=-\frac{5\pi }{36}+\frac{k2\pi }{3}\end{array}\right.(k\in Z)$

D. $\left[\begin{array}{l}x=-\frac{\pi }{36}+k2\pi \\ x=\frac{5\pi }{36}+k2\pi \end{array}\right.(k\in Z)$