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Homework Help: Periodic functions

  1. Dec 14, 2003 #1
    I'm doing a practice exam for a math test on thursday, wondering if anyone could help figure out how to get from one step to the next. i dont think that the background info is necessary for these two steps.

    the file is attached (Adobe acrobat).

    what i am wondering about is the answer under (2b).
    If the solution for finding (del)u(x,y) were lettered a through d (4 steps, i am wondering how the professer got from b to c.

    of course i have emailed him as well.

    Attached Files:

  2. jcsd
  3. Dec 14, 2003 #2
    Look in the last line of the 2b) paragraph.
    \Delta \frac{16}{\pi^4 kl(k^2+l^2)}sin(k \pi x)sin(l \pi y) = [/itex]
    [itex] \frac{16}{\pi^4 kl(k^2+l^2)}(-\pi^2 (k^2 + l^2)sin(k\pi x)sin(l\pi y))


    Last edited: Dec 14, 2003
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