\(\Leftrightarrow\left[{}\begin{matrix}-x+2x=\dfrac{\Pi}{2}-\dfrac{\Pi}{4}+k2\Pi\\-x-2x=\dfrac{1}{2}\Pi+k2\Pi-\dfrac{\Pi}{4}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{\Pi}{4}+k2\Pi\\x=-\dfrac{\Pi}{12}-\dfrac{k2\Pi}{3}\end{matrix}\right.\)