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Homework Help: Integral of an exponential function

  1. Sep 12, 2010 #1
    1. The problem statement, all variables and given/known data

    Hey guys.

    How do I solve this integral?

    http://img816.imageshack.us/img816/208/68315659.png [Broken]

    I've not been doing this for a long time :)

    Thanks a lot.


    2. Relevant equations



    3. The attempt at a solution
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Sep 12, 2010 #2
    Re: Integral

    Show some work, and explain what tools you have to work with. Definite integrals can be computed in many ways.
     
  4. Sep 12, 2010 #3
    Re: Integral

    You can use integration by parts. Using u = e^-t and dv = t^-2 dt
     
  5. Sep 12, 2010 #4
    Re: Integral

    Yeah, but then I'll get some kind of Ln(t)*e^-t, no?
     
  6. Sep 12, 2010 #5
    Re: Integral

    Actually you may want to check convergence.
     
  7. Sep 12, 2010 #6
    Re: Integral

    I was actually thinking:
    you perform integration by parts once to reduce t^2 to t.
    Result is that one of the terms is integral((e^-t)/t)
    Rewrite that term to become integral(1/te^t)

    use the following identity from integral tables: integral(ue^u) = (u-1)e^u
    the rest is taking limits.
     
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