Решите уравнение: \(\huge {cosx=-{{1} \over{2}}}.\)

• \(\huge {x= \pm {{ 2\pi} \over {3}} +{{ 2\pi k} }, k \in Z}\)
• \(\huge {x= \pm {{ \pi} \over {3}} +{{ 2\pi k} }, k \in Z}\)
• \(\huge {x= \pm {{ \pi} \over {6}} +{{ 2\pi k} }, k \in Z}\)
• \(\huge {x= \pm {{ 5\pi} \over {6}} +{{ 2\pi k} }, k \in Z}\)