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Homework Help: Integration-Problem with substitution

  1. Nov 12, 2009 #1
    1. The problem statement, all variables and given/known data
    I have reached this integration from a mechanics problem about small angle scattering. t= (2pa/mv^2)*(int from p to infinity) [r*dr]/[((b^2 +r^2)^(3/2))(sqrt(r^2 - p^2))]


    2. Relevant equations



    3. The attempt at a solution
    I know that there should be a substitution that will make this an easy problem, but I can't find it. I've tried the simple ones like let y=r^2, or y=b^2 + r^2, but they didn't get me anywhere.
     
  2. jcsd
  3. Nov 12, 2009 #2

    Mark44

    Staff: Mentor

    For further reference, here is your integral in a more readable form:
    [tex]\frac{2pa}{mv^2}\int_{r = p}^{\infty}\frac{r~dr}{(b^2 + r^2)^{3/2}\sqrt{r^2 - p^2}}[/tex]

    You might try an ordinary substitution of u = r2 - p2, but I'm not sure that will do you much good. Next I would try a trig substitution, sec [itex]\theta[/itex] = r/p.
     
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