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037 G
Lv 6
037 G asked in Science & MathematicsMathematics · 1 decade ago

Parsevall’s theorem?

Use Parsevall’s theorem to find E=∫[(sin 2πt/t)cos1000πt]² dt from – infinity to + infinity

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  • 1 decade ago
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    Parsevall's theorem says that the total integral (from -∞ to ∞) of any function's square is the same the integral of the square of its Fourier Transform.

    You must use the unitary form of the Fourier Transform. See:

    http://en.wikipedia.org/wiki/Fourier_transform#Def...

    So you have:

    1/√(2π) ∫ sin (2πt)cos1000πt) e^(-iωt) / t dt

    The result is X(ω), and then we just compute:

    ∫ X(ω) ² dω

    Both of those integrals are, of course, taken over the whole real line. So now we just have to evaluate them. I'm going to leave that up to you because I don't have the time or patience to work that out, and because I want you to do some of your homework on your own. But since no one else is answering except with "??" I wanted to try to at least guide you towards the answer.

  • 1 decade ago

    ??

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