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Homework Help: Deriving integral=arctan

  1. Oct 15, 2006 #1
    Yeah this one is good....

    Derive the following:

    int(1/(x^2 + a^2)dx = 1/a*arctan(x/a) + C

    any idea how I would derive this thing?
    Cause I'm totally lost....
     
  2. jcsd
  3. Oct 15, 2006 #2

    quasar987

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    Well do you agree that if you show that the derivative of 1/a*arctan(x/a) + C is 1/(x^2 + a^2, then you will have attained your goal?
     
  4. Oct 15, 2006 #3
    fundamental theorem of calculus
     
  5. Oct 15, 2006 #4
    no he actually wants us to plow thorugh the intregal using subsitution and stuff and then somehow end up at the answer
     
  6. Oct 15, 2006 #5
    use the substitution [tex] x = a\tan \theta [/tex]
     
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