| Line 2: | Line 2: | ||
<math> | <math> | ||
\lim_{x \to\ a}\frac{f(x)}{g(x)}= \lim_{x \to\ a}\frac{f'(x)}{g'(x)} | \lim_{x \to\ a}\frac{f(x)}{g(x)}= \lim_{x \to\ a}\frac{f'(x)}{g'(x)} | ||
| − | </math>, | + | </math>, <br> |
if the limis on the right exists (or is positive or negative infinity). | if the limis on the right exists (or is positive or negative infinity). | ||
This is Elizabeth's favorite theorem. | This is Elizabeth's favorite theorem. | ||
Revision as of 12:41, 4 September 2008
Suppose that f(a)=g(a)=0 and that f and g are differentiable on an open interval I containing a. Suppose also that g'(x)/=0 on I if x/=a. Then
$ \lim_{x \to\ a}\frac{f(x)}{g(x)}= \lim_{x \to\ a}\frac{f'(x)}{g'(x)} $,
if the limis on the right exists (or is positive or negative infinity).
This is Elizabeth's favorite theorem.
