Use Feynman's Trick for Evaluating Integrals 

Inactive can be used to derive identities by applying standard techniques such as Feynman's trick of differentiating under the integral sign.

Derive a closed form for by analyzing .

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First differentiating with respect to at produces the desired integral.

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If the integration is done first, the integral is simple.

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The derivative with respect to at is also straightforward.

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Equating the two expressions produces the answer.

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Verify the answer.

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