Giải các phương trình sau:

    \(1.\,\cos x = - \frac{{\sqrt 2 }}{2} \Leftrightarrow x = \pm \frac{{3\pi }}{4} + k2\pi \)

              \(2.\,\,\sin \left( {2x - \frac{\pi }{3}} \right) = \sin x \Leftrightarrow \left[ \begin{array}{l}2x - \frac{\pi }{3} = x + k2\pi \\2x - \frac{\pi }{3} = \pi - x + k2\pi \end{array} \right. \Leftrightarrow \left[ \begin{array}{l}x = \frac{\pi }{3} + k2\pi \\x = \frac{{4\pi }}{9} + \frac{{k2\pi }}{3}\end{array} \right.,k \in Z.\)