Results 1 to 3 of 3

Math Help - Evaluating an intergal

  1. #1
    Newbie
    Joined
    May 2014
    From
    Netherlands
    Posts
    1

    Evaluating an intergal

    Hello everyone,

    I was reading something and the following equation turns up:

     \int^T_0 e^{-rT}(T-t)dt = \frac{rT+e^{-rT}-1}{r^2}

    Where r is a constant. It has been a while since I last did integrals. When I tried to work it out I ended up with (expand the bracket and then integrate each term)

     \frac{e^{-rT}T^2}{2}

    I am fully willing to admit that I have made a stupid mistake somewhere as it has been a long time from when I last tried to solve one.

    Thank you for any help!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Prove It's Avatar
    Joined
    Aug 2008
    Posts
    11,591
    Thanks
    1445

    Re: Evaluating an intergal

    Is T a constant too?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor

    Joined
    Apr 2005
    Posts
    15,792
    Thanks
    1532

    Re: Evaluating an intergal

    Whether "T" is a constant or not since it is an upper limit on the integral it has to be treated as one.
    So the integral is Te^{-rT}\int_0^T dt- e^{-rt}\int_0^T tdt. I get the same thing you do. Perhaps the equation is not saying that the integral on the left gives the result on the right, but that the integral on the left is, for some other reason, equal to the right side? That is, that \frac{T^2e^{-rT}}{2}= \frac{rT- e^{-rT}- 1}{r^2}? That doesn't seem quite right but it is the only way I can make sense of it. Could you give more information about what you were reading?
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Intergal Question
    Posted in the Calculus Forum
    Replies: 7
    Last Post: October 25th 2013, 03:25 AM
  2. Line Intergal
    Posted in the Calculus Forum
    Replies: 2
    Last Post: August 21st 2011, 10:10 AM
  3. Intergal Question
    Posted in the Calculus Forum
    Replies: 6
    Last Post: May 7th 2010, 02:15 AM
  4. Iterated Intergal
    Posted in the Calculus Forum
    Replies: 2
    Last Post: March 29th 2010, 02:12 PM
  5. Tricky intergal... or is it?!
    Posted in the Calculus Forum
    Replies: 3
    Last Post: January 14th 2009, 03:23 PM

Search Tags


/mathhelpforum @mathhelpforum