On page 102 of Introduction to Quantum Mechanics, Griffiths writes that(adsbygoogle = window.adsbygoogle || []).push({});

[tex]\int_{-\infty}^{\infty}e^{i\lambda x}e^{-i \mu x}dx = 2\pi\delta(\lambda-\mu)[/tex]

I don't see how this follows. If you replace lambda with mu, then you get a cancellation, and the integral of 1dx. Am I missing something?

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# Orthogonal Integral

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