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!

Integral help

  1. Feb 1, 2008 #1
    how do i integrate 1/(x^2 +4)?

    please help
     
  2. jcsd
  3. Feb 1, 2008 #2
    What's the derivative of arctan?
     
  4. Feb 1, 2008 #3
    1/1+x^2
     
  5. Feb 1, 2008 #4
    See how that might be helpful?
     
  6. Feb 1, 2008 #5

    rock.freak667

    User Avatar
    Homework Helper

    [tex]\int \frac{1}{x^2 +4} dx[/tex]

    [tex] = \int \frac{1}{x^2 +(2)^2} dx[/tex]


    try x=2tan[itex]\theta[/itex]
     
  7. Feb 1, 2008 #6
    hmm lemem see...1 second
     
  8. Feb 1, 2008 #7
    Exactly.. so now from your function, you take 4 common, you get:

    [tex]
    \frac{1}{4}\int\frac{1}{({\frac{x}{2}})^2 + 1}dx
    [/tex]

    Now, if you take [itex]\frac{x}{2} = y[/itex].. you can solve this integral.. get a hint?

    Once you have done this, it would be helpful for you to remember the formula for a general case as in [tex]\int\frac{1}{a^2 + x^2}dx[/tex]
     
  9. Feb 1, 2008 #8
    Yeah rohan's post is what I was think too..
     
  10. Feb 1, 2008 #9
    oh i see, thanks

    and quick response from everyone =)
     
  11. Feb 2, 2008 #10
    [tex]\int\frac{1}{x^2+a^2}dx=\frac{1}{a}\arctan\frac{x}{a}+C[/tex]
    [tex]\int\frac{1}{x^2+2^2}dx=\frac{1}{2}\arctan\frac{x}{2}+C[/tex]
     
  12. Feb 2, 2008 #11
    No need to post the solution he all ready figured it out...
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Integral help
  1. Integral help (Replies: 4)

  2. Integration Help (Replies: 5)

  3. Integration help! (Replies: 3)

  4. Help with an integral (Replies: 1)

  5. Integrals help (Replies: 7)

Loading...