\(\cos 3x - \sin 2x - \cos x = 0\)
A.\(S = \left\{ {\frac{{k\pi }}{2};\frac{\pi }{6} + k2\pi ;\frac{{5\pi }}{6} + k2\pi |k \in Z} \right\}\)
B.\(S = \left\{ {\frac{{k\pi }}{2};\frac{{ - \pi }}{6} + k2\pi ;\frac{{7\pi }}{6} + k2\pi |k \in Z} \right\}\)
C.\(S = \left\{ {k\pi ;\frac{{ - \pi }}{6} + k2\pi ;\frac{{7\pi }}{6} + k2\pi |k \in Z} \right\}\)
D.\(S = \left\{ {k\pi ;\frac{\pi }{6} + k2\pi ;\frac{{5\pi }}{6} + k2\pi |k \in Z} \right\}\)