Date: Feb 20, 2013 11:13 PM
Author: William Elliot
Subject: Differentiability

A problem from
http://at.yorku.ca/cgi-bin/bbqa?forum=ask_an_analyst&task=list

   Suppose f(x)= e^(-1/x^2) for x not equal to 0, and f(0)=0.

   Without using l'hopital's rule, prove f is differentiable at 0 and
   that f'(0)=0.