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Homework Help: Need help finding the function of an expansion

  1. Aug 1, 2012 #1
    1. The problem statement, all variables and given/known data

    can anybody help with finding the function whos expansion is this -(5/16)x^7+(21/16)x^5-(35/16)x^3+(35/16)x

    I looks like a function of sin(X) but I just cant nail down what it is.

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Aug 1, 2012 #2


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    Have you looked at the graph?
    It doesn't look like a sine curve to me, more like a polynomial of some sort, heh heh.
  4. Aug 1, 2012 #3


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    What do you mean by "expansion"? Since you have powers of x I would have thought "Taylor's series" but the Taylor's series of any thing other than a polynomial is an infinite series. Any finite "expansion" in powers of x is just the polynomial it looks like. And if you mean this to be the first seven terms of a power series, you will have to tell us what the general coefficient is.
    Last edited by a moderator: Aug 2, 2012
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