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Homework Help: In terms of n 1, 1, -1, -1, 1, 1, -1, -1,

  1. May 12, 2010 #1
    1. The problem statement, all variables and given/known data

    Put in general terms 1, 1, -1, -1, 1, 1, -1, -1, ...

    2. Relevant equations



    3. The attempt at a solution

    obviously (-1)^n, alternates 1, -1, 1, -1...

    I have no idea how to figure this out. I thought it might have a sin function in it possibly.
    Thanks a lot for your help.
     
  2. jcsd
  3. May 12, 2010 #2

    jbunniii

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    If you defined a function f(n) such that

    f(0) = 0
    f(1) = 0
    f(2) = 1
    f(3) = 1
    f(4) = 2
    f(5) = 2
    ...

    then

    [tex](-1)^{f(n)}[/tex]

    would work, right? So try to find a simple formula for f(n).
     
  4. May 12, 2010 #3
    The [itex]i^{th}[/itex] term (starting with [itex]i=1[/itex]) could be [itex]\sqrt{2}sin\{(2i-1)\frac{\pi}{4}\}[/itex], but don't use that. You could probably use something similar to generate the [itex]f(i-1)[/itex] that jbunniii has suggested.

    Of course, if the first number after the dots start is 42 you're in trouble.
     
  5. May 12, 2010 #4
    Hey thx a lot for the help. Either method works fine, as long as you can figure out f(n) for the first one.
     
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