How Do You Solve This Complex Indefinite Integral?

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Discussion Overview

The discussion revolves around evaluating a complex indefinite integral involving a polynomial under a square root, specifically \(\int \frac{du}{ \sqrt{Au^{s+2}+Bu^2+Cu+D} }\), where \(s\) is a positive real number. Participants explore the feasibility of solving this integral using computer algebra systems and discuss specific cases for the variable \(s\).

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant seeks help in evaluating the integral without needing a manual solution, suggesting the use of a computer algebra system.
  • Another participant expresses doubt about the capability of Mathematica or other systems to solve the integral, suggesting that more specific variable definitions might help.
  • A participant specifies that \(s\) is a positive integer and provides a particular value for \(A\), while also suggesting to consider cases where \(s=1,2,3,4\).
  • It is noted that even for \(s=1\), the integral appears to be a complex elliptic integral, with a reference to Wolfram Alpha for evaluation.
  • Concerns are raised about the output from Wolfram Alpha, specifically questioning the meaning of the "Root" function in the context of the integral.
  • Another participant speculates that the "Root" notation may refer to a specific root of a high-degree polynomial but concludes that the integral is likely not solvable.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the solvability of the integral, with no consensus on whether it can be evaluated using computer algebra systems. Multiple viewpoints on the complexity of the integral and the interpretation of outputs from computational tools are presented.

Contextual Notes

Limitations include the lack of specific definitions for all variables involved and the unresolved nature of the integral's complexity across different values of \(s\). The discussion also highlights the potential ambiguity in the output from computational tools.

qspeechc
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Hi

I'm trying to evaluate the following indefinite integral, where s is any positive real number

[tex]\int \frac{du}{ \sqrt{Au^{s+2}+Bu^2+Cu+D} }[/tex]

For any A,B,C,D, and u is zero at [tex]\pm \infty[/tex] I don't need to know how to do it, you can evaluate it on some computer algebra system. Any help thanks?
 
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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.
 
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.
 
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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