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Homework Help: Derivative of exponential function

  1. Feb 13, 2007 #1
    1. The problem statement, all variables and given/known data
    find y', [tex] y = \frac{e^x}{1+e^x}[/tex]


    2. Relevant equations
    derivative of e^x = e^x, quotient rule.


    3. The attempt at a solution

    The old man is back, sorry, and I don't seem to be able to enter this using the tex stuff.
    This is from Kline's Calculus, page 348. I proceed as follows:

    y' = [(1+e^x)(e^x)-e^x(e^x)]/(1+e^x)^2 --- the quotient rule.

    Simplifying:

    y' = e^x/(1+e^x)^2

    However, Kline gives 1/(1+e^x).

    I am at a loss. Thanks for any suggestions.

    Sheldon
     
    Last edited: Feb 13, 2007
  2. jcsd
  3. Feb 13, 2007 #2

    mjsd

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    Homework Helper

    I believe your answer is correct
     
  4. Feb 13, 2007 #3

    Gib Z

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    Homework Helper

    You can check on www.calc101.com, it shows how derivatives are done. Your answer is correct, Klines books weren't very well edited >.<
     
  5. Feb 13, 2007 #4
    Thank you both very much. Also for the calc101 link.

    Sheldon
     
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