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Homework Help: Indefinite integral substitution

  1. Oct 20, 2006 #1
    evaluate the indefinite integral ((e^x)/((e^x)+1))dx

    I let u = ((e^x)+1)


    du = (e^x)dx

    which occurs in the original equation so..

    indefinite ingegral ((u^-1)du)

    taking the antiderivative I get 1 + C

    is this right? thanks!!
  2. jcsd
  3. Oct 20, 2006 #2
    [tex] \int \frac{e^{x}}{e^{x}+1} dx [/tex]

    it should be [tex] \ln|e^{x}+1| + C [/tex] because it is of the form [tex] \int \frac{du}{u}[/tex]
    Last edited: Oct 20, 2006
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