Giải phương trình

A. $\left[\begin{array}{l}x=\pm \frac{\pi }{3}+k2\pi \\ x=-\frac{\pi }{4}+k\pi \end{array}\right..$

B. $\left[\begin{array}{l}x=\pm \frac{\pi }{6}+k2\pi \\ x=-\frac{\pi }{6}+k\pi \end{array}\right..$

C. $\left[\begin{array}{l}x=\pm \frac{\pi }{3}+k\pi \\ x=-\frac{\pi }{4}+k2\pi \end{array}\right..$

D. $\left[\begin{array}{l}x=\pm \frac{\pi }{2}+k2\pi \\ x=\pm \frac{\pi }{4}+k\pi \end{array}\right..$