# L'hospital's rule

KLscilevothma
How to prove it? I've watched a tv program before and I vaguely remember the proof consists of 4 parts, which includes the mean value theorem, Cauchy's mean value theorem and the other 2 theorems. I haven't learned mean value theorem at that time and I didn't understand it, perhaps I can now.

Lonewolf
Check out http://mathforum.org/library/drmath/view/53340.html. It's a bit too large to type in the forum. The proof that uses Cauchy's mean value theorem begins

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Date: 12/23/98 at 11:43:47
From: Doctor Rob
Subject: Re: Proof of L'hopital's rule

The first proof uses Taylor expansions. The second uses Cauchy's MVT.

Originally posted by KL Kam
How to prove it? I've watched a tv program before and I vaguely remember the proof consists of 4 parts, which includes the mean value theorem, Cauchy's mean value theorem and the other 2 theorems. I haven't learned mean value theorem at that time and I didn't understand it, perhaps I can now.
http://archives.math.utk.edu/visual.calculus/3/index.html