lim

Tìm giới hạn
$a) \mathop {\lim }\limits_{x \to 0}(\frac{2}{\sin 2x}-\cot x ) $
$b) \mathop {\lim }\limits_{x \to 1} \frac{\sqrt{x+3}-2x }{\tan (x-1)} $
$c)\mathop {\lim }\limits_{x \to 0}[\tan 2x \tan (\frac{\pi}{4}-x  )] $
$d)\mathop {\lim }\limits_{x \to 0}[\frac{98}{83}(\frac{1-\cos 3x \cos 5x \cos 7x}{\sin^2 7x} )]$

Tìm giới hạn
$e)\mathop {\lim }\limits_{x \to 0}\frac{\cos^4 x -\sin^4 x -1}{\sqrt{x^2+1}-1 }  $
$f) \mathop {\lim }\limits_{x \to 0}\frac{\sin(\sin x)}{x}  $
$g) \mathop {\lim }\limits_{x \to 1}\frac{\sqrt{2x+1}-\sqrt[3]{x^2+1}  }{\sin x}  $
$h)\mathop {\lim }\limits_{x \to 0}\frac{\sqrt{\cos x}-\sqrt[3]{\cos x}  }{\sin^2 x}  $

Tìm giới hạn
$d) \mathop {\lim }\limits_{x \to 0}\frac{\sin 3x}{1-2\cos x}  $
$e) \mathop {\lim }\limits_{x \to 0}\frac{1-\cos 5x \cos 7x}{\sin^2 11x}  $
$f) \mathop {\lim }\limits_{x \to 0}\frac{\cos 12x-\cos 10x}{\cos 8x-\cos 6x}  $

Tìm giới hạn
$a)\mathop {\lim }\limits_{x \to 0}\frac{\tan x-\sin x}{x^3}  $
$b) \mathop {\lim }\limits_{x \to 0}\frac{1-\sin 2x-\cos 2x}{1+\sin 2x- \cos 2x}  $
$c) \mathop {\lim }\limits_{x \to 0} \frac{1-\cos^2 2x}{x\sin x} $