`~rai~`
\(2\cot x-\sqrt{3}=0\quad(1)\\ĐKXĐ:\sin x\ne 0\\\Leftrightarrow x\ne k\pi.(k\in\mathbb{Z})\\(1)\Leftrightarrow \cot x=\dfrac{\sqrt{3}}{2}\\\Leftrightarrow x=\text{arccot}\dfrac{\sqrt{3}}{2}+k\pi.(k\in\mathbb{Z})\\\text{Vậy S=}\left\{\text{arccot}\dfrac{\sqrt{3}}{2}+k\pi\Big|k\in\mathbb{Z}\right\}.\)