Tìm TXĐ của hàm số $y = tanx + cotx$

`~rai~`

\(y=\tan x+\cot x\\ĐKXĐ:\begin{cases}\cos x\ne 0\\\sin x\ne 0\end{cases}\\\Leftrightarrow \sin x\cos x\ne 0\\\Leftrightarrow 2\sin x\cos x\ne 0\\\Leftrightarrow \sin2x\ne 0\\\Leftrightarrow 2x\ne k\pi\\\Leftrightarrow x\ne k\dfrac{\pi}{2}.(k\in\mathbb{Z})\\TXĐ:D=\mathbb{R}\backslash\left\{k\dfrac{\pi}{2}\Big|k\in\mathbb{Z}\right\}.\)