1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Fourier series

  1. May 8, 2016 #1
    1. The problem statement, all variables and given/known data
    the answer that i get is different with the answer provided , is my answer wrong ? i got ( cos(2n -1) / 2n-1 )instead of ( cos(n+1) / n+1 )
    2CYgve2.jpg

    xH4yExE.jpg
    2. Relevant equations


    3. The attempt at a solution
     
    Last edited by a moderator: May 8, 2016
  2. jcsd
  3. May 8, 2016 #2

    vela

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Education Advisor

    It's easy enough to check yourself. Try plotting each series. You only need 4 or 5 terms each.

    www.desmos.com is useful if you don't have access to plotting software.
     
  4. May 9, 2016 #3
    I am not interested in the graph, I just wanna know the final answer....
     
  5. May 9, 2016 #4

    Samy_A

    User Avatar
    Science Advisor
    Homework Helper

    I actually followed vela's good advice, and the result is telling ...

    Another test you could try: what happens with the given solution (answer b) when x=π?
     
    Last edited: May 9, 2016
  6. May 9, 2016 #5
    Cos(n +1 ) pi= (-1)^n.... What can we conclude from that??
     
  7. May 9, 2016 #6

    Samy_A

    User Avatar
    Science Advisor
    Homework Helper

    No, that is not correct.
    ##\cos 2 \pi = \cos (1+1) \pi \neq {(-1)}^1##

    Once you have the correct values, plug them in into the Fourier series of answer (b).
     
  8. May 9, 2016 #7
    It's (-1) ^ (n +1)
     
  9. May 9, 2016 #8

    Samy_A

    User Avatar
    Science Advisor
    Homework Helper

    Correct.

    So what is the Fourier series of answer (b) for x=π? Does it converge? If so, to what value?

    And don't forget about vela's advice: it takes 2 minutes, and yields very interesting information.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Fourier series
  1. Fourier Series (Replies: 1)

  2. Fourier Series (Replies: 6)

  3. Fourier series (Replies: 1)

  4. Fourier Series (Replies: 10)

  5. Fourier series (Replies: 4)

Loading...