`~rai~`
\(\tan\dfrac{x}{2}=\sqrt{3}\quad(1)\\ĐKXĐ:\cos\dfrac{x}{2}\ne 0\\\Leftrightarrow\dfrac{x}{2}\ne \dfrac{\pi}{2}+m\pi\\\Leftrightarrow x\ne \pi+m2\pi.(m\in\mathbb{Z})\\(1)\Leftrightarrow \dfrac{x}{2}=\dfrac{\pi}{3}+k\pi\\\Leftrightarrow x=\dfrac{2\pi}{3}+k2\pi.(k\in\mathbb{Z})\\\text{Vậy S=}\left\{\dfrac{2\pi}{3}+k2\pi\Big|k\in\mathbb{Z}\right\}.\)