\(a,đk:\left\{{}\begin{matrix}sinx\ne0\\cosx\ne0\end{matrix}\right.\\ \Rightarrow\left\{{}\begin{matrix}x\ne k\pi\\x\ne\dfrac{\pi}{2}+k\pi\end{matrix}\right.\)
\(TXĐ:D=R/\left\{k\pi;\dfrac{\pi}{2}+k\pi\right\}\)
b, \(y=tanx-cotx=\dfrac{sinx}{cosx}-\dfrac{cosx}{sinx}\)
đk \(\left\{{}\begin{matrix}cosx\ne0\\sinx\ne0\end{matrix}\right.\)
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