l'Hôpital's rule (also spelled l'Hospital) uses derivatives to help compute limits with indeterminate forms. Application (or repeated applications) of the rule often converts an indeterminate form to a determinate form, allowing easy computation of the limit.

For f(x) and g(x) differentiable in a neighborhood of a.  If the limit (as x → a) of f(x) / g(x) is indeterminate of the type 0/0 or  ∞/∞: