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Homework Help: Integration Problem

  1. Aug 27, 2007 #1
    Hi
    I'm trying to integrate
    [tex]
    \int (-40x^3 + 38.4x^2 - 13.288x + 1.98072)\sqrt{14400x^4 - 18432x^3 + 9087.36x^2 - 2041.0368x+ 177.570944}dx
    [/tex]
    The way I thought I could do it was express the first part (the cubic) in terms of the derivative of the second and do it by substitution. Unfortunately it doesn't work. :frown:
    Not totally sure that it can be done at all.

    Thanks for any help!
     
  2. jcsd
  3. Aug 27, 2007 #2

    Dick

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    Homework Helper

    No, I don't think you are going to be able to integrate that in closed form. But there are simple numerical methods to consider like Simpson's rule.
     
  4. Aug 27, 2007 #3
    You can painfully do it by elliptic intehrals. But how did you arrive at this problem?
     
  5. Aug 27, 2007 #4
    I put it into maple, and the answer cannot be expressed with elementary functions (and the answer is about 19 lines!)
     
  6. Aug 28, 2007 #5
    Ok thanks people. I found the answer numerically. I arrived at the problem when trying to evaluate the surface of revolution of the cubic function.
     
  7. Aug 28, 2007 #6

    Gib Z

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    How did you evaluate an indefinite integral numerically :(
     
  8. Aug 28, 2007 #7
    Haha it was a definite integral, just didn't bother with the notation :-)
     
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