Question

txđ: \(y=\frac{tan2x}{cosx}\)

Answer 1

\(\left\{{}\begin{matrix}\cos2x\ne0\\\cos x\ne0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}2x\ne\frac{\pi}{2}+k\pi\\x\ne\frac{\pi}{2}+k\pi\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x\ne\frac{\pi}{4}+\frac{k\pi}{2}\\x\ne\frac{\pi}{2}+k\pi\end{matrix}\right.\Leftrightarrow x\ne\frac{k\pi}{4}\)