Tìm tập xác định y = căn 2 + cos x / 1 - sin 2x

$\begin{array}{l} y = \sqrt {\frac{{2 + \cos x}}{{1 - \sin 2x}}} \\ DK:\frac{{2 + \cos x}}{{1 - \sin 2x}} \ge 0\,\left( * \right)\\ Ta\,co:\,2 + \cos x > 0,\forall x\,(do\,\cos x \ge - 1\,nen\,2 + \cos x \ge 2 - 1 = 1)\\ Khi\,do\,\left( * \right) \Leftrightarrow 1 - \sin 2x > 0 \Leftrightarrow \sin 2x < 1 \Leftrightarrow \sin 2x \ne 1\,\left( {do\,\sin 2x \le 1,\forall x} \right)\\ \Leftrightarrow 2x \ne \frac{\pi }{2} + k2\pi \Leftrightarrow x \ne \frac{\pi }{4} + k\pi \end{array}$

$y=\dfrac{\sqrt2 + \cos x}{1-\sin 2x}$

ĐK: $1-\sin 2x\neq 0$

$\Leftrightarrow \sin 2x\neq 1$

$\Leftrightarrow 2x\neq \dfrac{\pi}{2}+k2\pi$

$\Leftrightarrow x\neq \dfrac{\pi}{4}+k\pi$

$D=\mathbb{R}$ \ $\{\dfrac{\pi}{4}+k\pi\}$