I'm a high school senior. I'm in ap calculus and was wondering if you know the proof of L'Hopital's Rule? Our teacher said he has never been able to find it in a math book and was unable to derive it himself.


Hi Mike,

The key to the proof of L'Hopital's Rule is a generalization of the Mean Value Theorem. We received a question a while ago from another student named Kay who was looking for a proof of this generalization. We posted an outline of the proof and an indication of how this can be used to prove L'Hopital's Rule. It is question 1 of the three questions that Kay sent us.

Let us know if we can be of any further help.
La centrale des maths