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Thread: Fourier series

  1. #1
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    Fourier series

    Define $\displaystyle f(t)=e^{-t} on [-\pi,\pi) $ and extend f to be $\displaystyle 2\pi$-periodic.Find the complex Fourier series of f.
    Then, apply Parseval's relation to f to evaluate $\displaystyle /sum {1/(1+k^2)} $.
    I know how the complex fourier series looks like but I don't know how to extend it periodically
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  2. #2
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    Quote Originally Posted by AkilMAI View Post
    Define $\displaystyle f(t)=e^{-t} on [-\pi,\pi) $ and extend f to be $\displaystyle 2\pi$-periodic.Find the complex Fourier series of f.
    Then, apply Parseval's relation to f to evaluate $\displaystyle /sum {1/(1+k^2)} $.
    I know how the complex fourier series looks like but I don't know how to extend it periodically
    The function $\displaystyle e^{t}$ is not peroidic, but when you find its Fourier series on $\displaystyle [-\pi,\pi)$ and then let $\displaystyle t \in \mathbb{R}$ not just the interval you will be a new function that is periodic on all of $\displaystyle \mathbb{R}$ (It will just be translated copies of the series on the original interval)
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    Quote Originally Posted by AkilMAI View Post
    Define $\displaystyle f(t)=e^{-t} on [-\pi,\pi) $ and extend f to be $\displaystyle 2\pi$-periodic.Find the complex Fourier series of f.
    Then, apply Parseval's relation to f to evaluate $\displaystyle /sum {1/(1+k^2)} $.
    I know how the complex fourier series looks like but I don't know how to extend it periodically
    http://www.mathhelpforum.com/math-he...em-167764.html

    Kind regards

    $\displaystyle \chi$ $\displaystyle \sigma$
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    Quote Originally Posted by AkilMAI View Post
    Define $\displaystyle f(t)=e^{-t} on [-\pi,\pi) $ and extend f to be $\displaystyle 2\pi$-periodic.Find the complex Fourier series of f.
    Then, apply Parseval's relation to f to evaluate $\displaystyle /sum {1/(1+k^2)} $.
    I know how the complex fourier series looks like but I don't know how to extend it periodically
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