Giải phương trình \(\cos x = \frac{{\sqrt 3 }}{2}\).

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

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

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

D. \(\left[ \begin{array}{l}
x = \frac{\pi }{6} + k2\pi \\
x = \frac{{5\pi }}{6} + k2\pi 
\end{array} \right.,k \in Z.\)