View Full Version : Stubborn Integral
qspeechc
Oct30-09, 04:58 AM
Hi
I'm trying to evaluate the following indefinite integral, where s is any positive real number
\int \frac{du}{ \sqrt{Au^{s+2}+Bu^2+Cu+D} }
For any A,B,C,D, and u is zero at \pm \infty I don't need to know how to do it, you can evaluate it on some computer algebra system. Any help thanks?
Mathematica can't do it, doubt any other computer systems will be able to either. If you could specify more of your variables it might help.
qspeechc
Oct30-09, 08:35 AM
Ok, s is a positive integer, and A=-1/(1+s)(2+s), that's as specific as I can get. Or, simply looking at the cases s=1,2,3,4. Thanks.
Even if s=1 it seems like a very complex elliptic integral.
The simplest it can be made into is evaluated by Mathematica if you enter "integrate 1/( x^3+ ax^2+bx+c)^(1/2) dx" into www.wolframalpha.com .
I've never seen that "Root" function or notation before though.
qspeechc
Oct30-09, 08:54 AM
Er, yea, wolframalpha gives a strange answer, what is # supposed to represent? But thanks anyway.
I think it may signify a certain root of a high degree polynomial. Although I can't make out more than that. Sorry, I think that integral you have is pretty much not doable.
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