ĐK tự làm
PT $\Leftrightarrow 4(\sqrt 3 \sin x+\cos x) +\dfrac{2}{\sin 2x}=4\dfrac{\cos 2x }{\sin 2x}$
$\Leftrightarrow 2(\sqrt 3 \sin x+\cos x)\sin 2x +1 =2\cos 2x$
$\Leftrightarrow 2(\sqrt 3 \sin x+\cos x)\sin 2x +\sin^2 x +\cos^2 x=2(\cos^2 x-\sin^2 x)$
$\Leftrightarrow 2(\sqrt 3 \sin x+\cos x)\sin 2x +3\sin^2 x -\cos^2 x=0$
$\Leftrightarrow (\sqrt 3 \sin x+\cos x)(2\sin 2x +\sqrt 3\sin x -\cos x)=0$ Dễ rồi