(1,0 điểm)

Câu hỏi: (1,0 điểm)

A x = {\frac{\pi }{6}+k2\pi ;\frac{5\pi }{6}+k2\pi ;k2\pi ;\frac{2\pi }{3}+k2\pi}

B x = {-\frac{\pi }{6}+k2\pi ;\frac{7\pi }{6}+k2\pi ;k2\pi ;\frac{2\pi }{3}+k2\pi}

C x = {-\frac{\pi }{6}+k2\pi ;\frac{7\pi }{6}+k2\pi ;k2\pi}

D x = {\frac{\pi }{6}+k2\pi ;\frac{7\pi }{6}+k2\pi ;\frac{2\pi }{3}+k2\pi}