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Homework Help: Integration by reduction

  1. Nov 8, 2007 #1
    1. The problem

    Show that [tex]\int^{1}_{0}x^{m}(1-x)^{n} dx = \frac{m!n!}{(m+n+1)!}[/tex] for all integers [tex]m, n \geq 0[/tex]

    The question is under "Reduction" topic, so I assume we solve this via reduction.

    2. My attempt

    My attempt is as follows:

    Let [tex]x = cos^{2}x[/tex]

    Then we get [tex]\frac{1}{2}\int cos^{2m-1}sin^{2n-1}dx[/tex]

    From here I use the reduction formula: [tex]I_{m, n} : \frac{m-1}{m+n} : m \geq 2
    [/tex] or [tex]\frac{n-1}{m+n} : n \geq 2[/tex]

    It seems like I am on the right track, but it's not working out properly. Am I missing something?
  2. jcsd
  3. Nov 8, 2007 #2
    don't really know how to help but...

    wow. that looks like a monster problem! what hideousness of an equation that is!
  4. Nov 8, 2007 #3
    Solve using integration by parts. You should get a redundant term or otherwise be able to simplify the problem in a few steps. The substitution method looks unnecessarily complicated here, and that too is based on integration by parts...so you'd be better off trying this problem from the basics up.
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