Nghiệm của phương trình sin2x + cosx = 0 là A. x =  -pi /2 + kpi ; x =  - pi /6 + k2pi /3 .( k thuộc Z);

\(\left[ \begin{array}{l}x = - \frac{\pi }{2} + k\pi \\x = - \frac{\pi }{6} + \frac{{k2\pi }}{3}\end{array} \right.\left( {k \in \mathbb{Z}} \right)\);

\(\left[ \begin{array}{l}x = - \frac{\pi }{2} + k2\pi \\x = \frac{\pi }{2} + \frac{{k2\pi }}{3}\end{array} \right.\left( {k \in \mathbb{Z}} \right)\);

\(\left[ \begin{array}{l}x = \frac{\pi }{2} + k2\pi \\x = \frac{\pi }{6} + \frac{{k\pi }}{3}\end{array} \right.\left( {k \in \mathbb{Z}} \right)\);

\(\left[ \begin{array}{l}x = - \frac{\pi }{2} + k\pi \\x = \frac{\pi }{4} + k2\pi \end{array} \right.\left( {k \in \mathbb{Z}} \right)\).