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I must have hit my head

  1. Sep 12, 2007 #1
    because I keep getting jammed up here,

    Using u substitution

    [tex]\int \frac{dx}{e^x}[/tex] I don't see what else to let u equal besides e^x. .....
     
  2. jcsd
  3. Sep 12, 2007 #2

    learningphysics

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    Take the denominator to the top...
     
  4. Sep 12, 2007 #3
    I just got it I think.....Like I said, somehow since last night I've lost brain cells!:grumpy: for some reason I wouldn't belive that d\dx [e^-x]=e^-x <---
    that is correct though right?
    what is the derivative of e^-x ?
     
    Last edited: Sep 12, 2007
  5. Sep 12, 2007 #4

    learningphysics

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    almost. be careful about the '-'

    You should use the chain rule: what is the derivative of e^(ax)
     
  6. Sep 12, 2007 #5
    is it ae^ax ?

    so it should be [tex]-e^{-x}[/tex]
     
  7. Sep 12, 2007 #6
    Just checked the answer and it is right. Thanks. Strange that I forgot to chain rule.
     
  8. Sep 12, 2007 #7

    learningphysics

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    no prob.
     
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