-\frac{\sqrt3}{2};\\ \cos2x=-\frac{\sqrt3}{2};\\ \cos2x=\pm\frac{5\pi}{6}+2\pi n,\n\in Z;\\ -\frac{5\pi}{6}+2\pi n<2x<\frac{5\pi}{6}+2\pi n;\\ -\frac{5\pi}{12}+\pi n<x<\frac{5\pi}{12}+\pi n;\\ \\ \\ x\in\left(-\frac{5\pi}{12}+\pi n;\frac{5\pi}{12}+\pi n\right),\ n\in Z." alt="\cos2x>-\frac{\sqrt3}{2};\\ \cos2x=-\frac{\sqrt3}{2};\\ \cos2x=\pm\frac{5\pi}{6}+2\pi n,\n\in Z;\\ -\frac{5\pi}{6}+2\pi n<2x<\frac{5\pi}{6}+2\pi n;\\ -\frac{5\pi}{12}+\pi n<x<\frac{5\pi}{12}+\pi n;\\ \\ \\ x\in\left(-\frac{5\pi}{12}+\pi n;\frac{5\pi}{12}+\pi n\right),\ n\in Z." align="absmiddle" class="latex-formula">