How can the Fourier Integral Theorem be used to evaluate improper integrals?

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Homework Help Overview

The discussion revolves around evaluating an improper integral using the Fourier Integral Theorem. The specific integral in question involves the cosine function and a parameter alpha, with the goal of demonstrating a relationship to an exponential function.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants attempt to express the cosine function in terms of exponential functions and consider the use of contour integrals and the residue theorem. There are questions regarding the application of the Fourier Integral Theorem and its definition.

Discussion Status

Some participants have shared their initial attempts at expressing the cosine function, while others are exploring the definition and implications of the Fourier Integral Theorem. There is an ongoing exploration of methods, but no consensus or resolution has been reached yet.

Contextual Notes

Participants note the requirement to evaluate the integral directly using the Fourier Integral Theorem, which raises questions about the theorem's specifics and how it applies to the given problem.

Fusiontron
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Homework Statement



Show that

integral from 0 - > infinity (cos(alpha*x)/(alpha^2 + 1))dalpha = (pi/2)exp(-x)

Homework Equations





The Attempt at a Solution



cos(alpha*x) = (1/2)(exp(i*alpha*x)+exp(-i*alpha*x))

Really don't know where to go from here.
 
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Fusiontron said:

Homework Statement



Show that

integral from 0 - > infinity (cos(alpha*x)/(alpha^2 + 1))dalpha = (pi/2)exp(-x)

Homework Equations





The Attempt at a Solution



cos(alpha*x) = (1/2)(exp(i*alpha*x)+exp(-i*alpha*x))

Really don't know where to go from here.

Use contour integrals and the residue theorem. A lot of Fourier integrals need to be done that way.
 
The problem says to evaluate directly with the Fourier Integral Theorem.
 
Fusiontron said:
The problem says to evaluate directly with the Fourier Integral Theorem.

Ok, so what is the Fourier Integral Theorem?
 

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