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[tranwhy]

Tinh: $ \lim_{x \rightarrow 0} \frac{ x}{sinx} $

Edited by tranwhy, 20-04-2016 - 16:27.

[quangtq1998]

Tinh: $ \lim_{x \rightarrow 0} \frac{ x}{sinx} $

 
ta có : 
$ \lim_{x \rightarrow 0} \frac{ f(x)}{g(x)}= $$ \lim_{x \rightarrow 0} \frac{ f'(x)}{g'(x)}$ nếu  $f(0) = g(0) = 0 $
Thật vậy :
$ \lim_{x \rightarrow 0} \frac{ f(x)}{g(x)}$$ = \lim_{x \rightarrow 0} \frac{ \frac{f(x) -f(0)}{x-0}}{\frac{g(x)-g(0)}{x-0}}$$ =\lim_{x \rightarrow 0} \frac{ f'(x)}{g'(x)}$
do đó :
$L = 1$

Edited by quangtq1998, 22-08-2016 - 15:30.