Mai em nộp r giúp với ạ

1) $y = \dfrac{\tan x}{\sqrt{1 - \cos x}}$

$y$ xác định

$\Leftrightarrow \begin{cases}\cos x \ne 0\\\cos x \ne 1\end{cases}$

$\Leftrightarrow \begin{cases}x \ne \dfrac{\pi}{2} + k\pi\\x \ne k2\pi\end{cases} \quad (k \in \Bbb Z)$

$\Rightarrow TXD: D = R\backslash\left\{\dfrac{\pi}{2} + k\pi; \, k2\pi \, |\, k\in \Bbb Z\right\}$

2) $y = \cot x.\sqrt{\dfrac{2 + \cos x}{1 - \sin x}}$

$y$ xác định

$\Leftrightarrow \begin{cases}\sin x \ne 0\\\sin x \ne 1\end{cases}$

$\Leftrightarrow \begin{cases}x \ne k\pi\\x \ne \dfrac{\pi}{2} + k2\pi\end{cases} \quad (k \in \Bbb Z)$

$\Rightarrow TXD: D = R\backslash\left\{k\pi; \,\dfrac{\pi}{2} + k2\pi\, |\, k\in \Bbb Z\right\}$

3) $\dfrac{3 - 2\cot\left(x - \dfrac{\pi}{4}\right)}{-2 + \sin x}$

$y$ xác định

$\Leftrightarrow \sin\left(x - \dfrac{\pi}{4}\right) \ne 0$

$\Leftrightarrow x \ne \dfrac{\pi}{4} + k\pi \quad (k \in \Bbb Z)$

$\Rightarrow TXD: D = R\backslash\left\{\dfrac{\pi}{4} + k\pi\, |\,k \in \Bbb Z\right\}$

4) $\dfrac{3 - 2\tan\left(x - \dfrac{\pi}{4}\right)}{2 + \sin x}$

$y$ xác định

$\Leftrightarrow \cos\left(x - \dfrac{\pi}{4}\right) \ne 0$

$\Leftrightarrow x \ne \dfrac{3\pi}{4} + k\pi \quad (k \in \Bbb Z)$

$\Rightarrow TXD: D = R\backslash\left\{\dfrac{3\pi}{4} + k\pi\, |\, k \in \Bbb Z\right\}$