Integral of sqrt(x^2-a^2)exp(-x)

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Discussion Overview

The discussion revolves around the integral of the function sqrt(x^2-a^2)exp(-x), exploring methods for its evaluation, including potential techniques and challenges associated with finding a closed-form solution.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested, Mathematical reasoning

Main Points Raised

  • One participant expresses difficulty in finding a formula for the integral, seeking guidance from others.
  • Another suggests using integration by parts and mentions a standard formula for integrating sqrt(x^2-a^2), which may aid in the process.
  • A participant asserts that a primitive (antiderivative) for the integral may not exist.
  • Another participant confirms that computational tools like Wolfram Alpha also struggle with this integral.
  • One participant proposes that numerical integration might be necessary for specific values of a, given the complexity of the integral.
  • A later reply indicates that the integral from a to infinity can be related to a modified Bessel function of the first kind.

Areas of Agreement / Disagreement

Participants express differing views on the possibility of finding a closed-form solution, with some suggesting numerical methods while others reference special functions. No consensus is reached regarding the existence of a primitive for the integral.

Contextual Notes

Participants note the challenges associated with integration techniques and the potential need for numerical methods, indicating that the integral's complexity may depend on the parameter a.

Who May Find This Useful

This discussion may be of interest to those studying advanced calculus, mathematical physics, or applied mathematics, particularly in the context of integrals involving exponential functions and square roots.

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New to the forum, thanks for having me.

I've looked in tables and tried Mathmatica but have not came
up with a formula for the integral over x of

sqrt(x^2-a^2)exp(-x)

If anyone could point me in the right direction I'd be appreciative.
Thanks
 
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[tex]\int\sqrt{x^2-a^2}e^{-x}dx[/tex]

Integration by parts?

There is a standard formula for integrating [tex]\int\sqrt{x^2-a^2}dx[/tex] (that involves logs which might help later with the exponential).

Haven't worked it out myself but that's where i'd start.
 
You won't be able to find a primitive.
 
yeah. wolfram didn't like it when i plugged it in.
 
Thanks for your help. Seems integration by parts will just require further integrals
of the form (x^2-a^2)^n/2 exp(-x). Maybe I'll just have to integrate numberially for fixed values of a.
 
The integral from a to infinity can be expressed in terms of a modified Bessel function of the first kind.
 

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