Hello,

Looking at which frequency l'Hôpital's rule is used, i'd like to know what is its real utility... D'you have examples where we HAVE to use it ? And can't use anything else ?

As a memento :

If $\displaystyle \lim_{x \to a} f(x)=\lim_{x \to a} g(x)=0 \text{\ or \ } \infty$, then :

$\displaystyle \lim_{x \to a} \frac{f(x)}{g(x)}=\lim_{x \to a} \frac{f'(x)}{g'(x)}$