Giải các phương trình sau:a) \(\cos 2x - 5\sin x -...

Câu hỏi: Giải các phương trình sau:a) \(\cos 2x - 5\sin x - 3 = 0\).                                                 b) \(\left[ {1 + \cos \left( {x + \frac{\pi }{2}} \right)} \right]{\tan ^2}x - \cos x = 1\).

A a)\(\left\{ { - \frac{\pi }{6} + k2\pi ;\frac{{7\pi }}{6} + k2\pi ,k \in Z} \right\}\).

b)\(\left\{ {\pi  + k2\pi ; - \frac{\pi }{4} + k\pi ,k \in Z} \right\}\).

B a)\(\left\{ { - \frac{\pi }{6} + k2\pi ;\frac{{11\pi }}{6} + k2\pi ,k \in Z} \right\}\).

b)\(\left\{ {\pi  + k2\pi ; - \frac{\pi }{2} + k\pi ,k \in Z} \right\}\).

C a)\(\left\{ { - \frac{\pi }{9} + k2\pi ;\frac{{7\pi }}{6} + k2\pi ,k \in Z} \right\}\)

b)\(\left\{ {\pi  + k2\pi ; - \frac{\pi }{4} + k\pi ,k \in Z} \right\}\).

D a)\(\left\{ { - \frac{\pi }{6} + k2\pi ;\frac{{7\pi }}{5} + k2\pi ,k \in Z} \right\}\).

b)\(\left\{ {\pi  + k2\pi ; - \frac{\pi }{4} + k\pi ,k \in Z} \right\}\).