Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Derivative using l'hopital's rule

  1. Apr 29, 2010 #1
    let f(x)

    exp(-1/x) for x>0, 0 for x<=0

    i want to get f'(x) by using l'hopital's rule, but somehow

    i'm applying l'hopital's rule again and again and no clear value is coming out.

    i know f'(0) is 0, but i cannot prove it
     
  2. jcsd
  3. Apr 29, 2010 #2
    So, using the definition of the derivative, you're looking for the limit as x-->0 of exp(-1/x)/x.

    If you use L'Hopital on this, you get that it is equal to the limit as x-->0 of -exp(-1/x)/x.

    So...?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook