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Fourier series

  1. Apr 13, 2016 #1
    1. The problem statement, all variables and given/known data
    is the author wrong ? i was told that the f(x) = 0.5(a_0) +Σ(a_n)cos (nπx / L ) ........ but , in the example(photo2) , the author ignore the L , which the author gave f(x) = 0.5(a_0) +Σ(a_n)cos (nπx ) +......

    2. Relevant equations


    3. The attempt at a solution
    P/ s : i have tried to make some correction beside the working , is it correct ?
     

    Attached Files:

    Last edited: Apr 13, 2016
  2. jcsd
  3. Apr 14, 2016 #2

    BvU

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    Don't know what photo 2 is, but in 154002 the author carefully uses L = 2.
    And in 1550002 L is ##\pi##
     
  4. Apr 14, 2016 #3
    So, the author is wrong, right? In155002, the L should be 2, right??
     
  5. Apr 14, 2016 #4

    BvU

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    If 150 says ##n\pi\x\over L## and 154 says ##n\pi\over 2##, doesn't that mean the author did take L = 2 ?

    As for 155, I'm not so sure: does the definition in your book agree with

    The Fourier series of the function f(x) is given by
    $$f(x)={a_0\over 2}+\sum_{n=1}^\infty \{a_n\cos nx+b_n\sin nx\}$$
    where the Fourier coefficients ##a_0##, ##a_n##, and ##b_n## are defined by the integrals$$
    a_0={1\over \pi} \int _{−\pi}^\pi f(x)\, dx,\quad a_n={1\over \pi} \int _{−\pi}^\pi f(x)\cos nx\,dx,\quad b_n{1\over \pi} \int _{−\pi}^\pi f(x)\sin nx\,dx$$
     
  6. Apr 14, 2016 #5
    no , as you can see it 150 , the author gave $$f(x)={a_0\over 2}+\sum_{n=1}^\infty \{a_n\cos nπx / L+b_n\sin nπx\/L}$$
     

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