ĐK: \(x\ne\dfrac{\pi}{4}+\dfrac{k\pi}{2}\)
\(cot2x\left(2cotx-2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}cot2x=0\\cotx=1\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{k\pi}{2}\\x=\dfrac{\pi}{4}+k\pi\end{matrix}\right.\)