Hints in solving this analitically?

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Discussion Overview

The discussion revolves around the integral \(\int_{-\infty}^{+\infty}\frac{e^{-x^2}}{\sqrt{x^2+1}}dx\), with participants exploring methods for solving it analytically and providing hints for the original poster who has calculated it numerically.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant suggests that the integral cannot be expressed purely in terms of analytic functions, proposing instead to express the answer using the modified Bessel function of the second kind, \(K_0\).
  • Another participant introduces the idea of relating the integral to a form involving the cosine and the hyperbolic sine, indicating a connection to the Digamma function.
  • A different viewpoint emphasizes that while an analytical solution is challenging, a series expansion could be attempted, though it may become complex.
  • One participant later corrects their previous statement, indicating that solving numerically might be a more practical approach than seeking an analytical solution, while also acknowledging uncertainty about the original poster's expertise.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether an analytical solution is feasible, with some suggesting it is possible through special functions while others argue that numerical methods may be more appropriate.

Contextual Notes

Participants express limitations regarding the complexity of the integral and the potential difficulty in finding a straightforward analytical solution, highlighting the dependence on special functions and series expansions.

Petr Mugver
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[tex]\int_{-\infty}^{+\infty}\frac{e^{-x^2}}{\sqrt{x^2+1}}dx[/tex]

I calculated it numerically, but I need an exact number. Hints?
 
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Well you can't express the answer purely by analyctic functions, but you could write the answer like this[tex]I \, = \sqrt{e} \, K_0 \left( \frac{1}{2} \right)[/tex]

Where K_0 is the modified Bessel function of the second kind.

Or use the MejerG function to express the answer.
 
Last edited:
You can start by noticing that this is really another form of:

[tex] \int_{0}^{\infty }cos(x sinh (t))dt[/tex]

Which is itself a special case of the Digamma function when v=0.

In any case, it's not easy to integrate it. You could try a series expansion centered at x=0, but it gets really messy. Your best bet is analytically. Otherwise, try starting with the Digamma function.
 
I was not able to edit my previous post for some reason. i meant to say that your best bet is to solve numerically, not analytically. But of course, we don't know your level of expertise with these kinds of integrals.
 

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