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Homework Help: Integration problem

  1. May 6, 2010 #1
    1. The problem statement, all variables and given/known data

    evaluate [tex]\int \frac{1}{x^2+1} dx[/tex]


    2. Relevant equations



    3. The attempt at a solution

    This cant be [tex]\frac{\ln x^2+1}{2x}[/tex] , my first thought on this .

    Then , i tried partial fraction , it didn't work either .
     
  2. jcsd
  3. May 6, 2010 #2

    Mark44

    Staff: Mentor

    Re: integration

    Your first thought led you to try an ordinary substitution, u = x^2 + 1. This won't work, though, because du = 2xdx, so there's no way to change the given integrand to du/u.

    If you know a derivative formula for which d/dx(something) = 1/(x^2 + 1) then that will be helpful in this problem. If you don't know or don't remember such a formula, a trig substitution will be the way to go, with tan u = x/1.
     
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