1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook