Giaỉ phương trình 

Câu hỏi: Giaỉ phương trình $\sin 2x={\cos }^4\frac{x}{2}-{\sin }^4\frac{x}{2}$.

A. $\left[\begin{array}{l}x=\frac{\pi }{6}+k2\pi \\ x=\frac{\pi }{2}+k2\pi \end{array}\right.$

B. $\left[\begin{array}{l}x=\frac{\pi }{4}+k\frac{\pi }{2}\\ x=\frac{\pi }{2}+k\pi \end{array}\right.$

C. $\left[\begin{array}{l}x=\frac{\pi }{3}+k\pi \\ x=\frac{3\pi }{2}+k2\pi \end{array}\right.$

D. $\left[\begin{array}{l}x=\frac{\pi }{12}+k\frac{\pi }{2}\\ x=\frac{3\pi }{4}+k\pi \end{array}\right.$