Giải thích các bước giải:
e.Ta có:
$\cos x=-\dfrac13$
$\to \sin^2x=1-\cos^2x=\dfrac89$
Mà $\pi<x<\dfrac{3\pi}{2}\to \sin x<0$
$\to \sin x=\dfrac{-2\sqrt{2}}{3}$
$\to \cot x=\dfrac{\cos x}{\sin x}=\dfrac{\sqrt{2}}{4}$
Ta có:
$E=\dfrac{4\cot x+1}{1-3\sin x}$
$\to E=\dfrac{4\cdot \dfrac{\sqrt{2}}{4}+1}{1-3\cdot \dfrac{-2\sqrt{2}}{3}}$
$\to E=\dfrac{\sqrt{2}+1}{1+2\sqrt{2}}$
