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Math Help - Fourier series (Whats wrong?)

  1. #1
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    Question Fourier series (Whats wrong?)

    I keep getting these answers wrong, which part is wrong id love some help.

    For mathqs1......Q2 i have also tried 18 and 27

    For mathqs2..... Q5 i have also tried 0

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    Attached Thumbnails Attached Thumbnails Fourier series (Whats wrong?)-mathqs1.png   Fourier series (Whats wrong?)-mathqs2.png  
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  2. #2
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    Re: Fourier series (Whats wrong?)

    Quote Originally Posted by Brennox View Post
    I keep getting these answers wrong, which part is wrong id love some help.

    For mathqs1......Q2 i have also tried 18 and 27

    For mathqs2..... Q5 i have also tried 0

    Please view attached cheers
    For S_2(x) you should enter a formula something like a+b \sin(x) + c \cos(x) + d \sin(2x) + e \cos(2x) where a,b,c,d,e are numerical values you have calculated from the function and Fourier series definitions.

    .
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  3. #3
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    Re: Fourier series (Whats wrong?)

    Quote Originally Posted by Brennox View Post
    I keep getting these answers wrong, which part is wrong id love some help.

    For mathqs1......Q2 i have also tried 18 and 27

    For mathqs2..... Q5 i have also tried 0

    Please view attached cheers
    For question 5 you want to evaluate:

    a_n=\frac{1}{\pi}\int_{-\pi}^{\pi}f(t) \cos(nt)\;dt = \frac{2}{\pi} \int_{0}^{\pi}f(t) \cos(n t)\;dt

    The last term is because f(t) is the even extension of f(t) defined on (0,\pi).

    .
    Last edited by zzephod; May 16th 2013 at 11:27 PM.
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  4. #4
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    Re: Fourier series (Whats wrong?)

    Quote Originally Posted by zzephod View Post
    For S_2(x) you should enter a formula something like a+b \sin(x) + c \cos(x) + d \sin(2x) + e \cos(2x) where a,b,c,d,e are numerical values you have calculated from the function and Fourier series definitions.

    .
    yeah i did that but got the wrong answer can you try it?
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  5. #5
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    Re: Fourier series (Whats wrong?)

    Quote Originally Posted by Brennox View Post
    yeah i did that but got the wrong answer can you try it?
    a_n=\frac{1}{\pi}\int_{-\pi/2}^{\pi/2}9\times \cos(nt)\;dt=\frac{18\,\sin\left( \frac{\pi\,n}{2}\right) }{\pi\,n}

    which can be simplified further, and because you have an even function all b_n=0
    Last edited by zzephod; May 17th 2013 at 07:22 AM.
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