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How to find the taylor for sin(x)^2 w/ sin(x), is this right?

  1. Oct 6, 2008 #1
    1. The problem statement, all variables and given/known data

    sin(x)= sum((-1)^k* (x^(2k+1)/(2k+1)!))k=0 to infinity

    2. Relevant equations

    so if i want to find sin(x)^2, (not sin(x^2), that would be easier though...)

    3. The attempt at a solution
    then...
    do i square the whole thing, like this?

    sum(((-1)^k* (x^(2k+1)/(2k+1)!))^2)k=0 to infinity

    thanks a bunch!
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Oct 7, 2008 #2

    Dick

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    Science Advisor
    Homework Helper

    You have to square the whole series (x-x^3/3!+x^5/5!-...)*(x-x^3/3!+x^5/5!-...). It's not just the sum of the squares of each term. It's a double sum. There are cross terms. It's easy enough to find the first few terms that way.
     
  4. Oct 7, 2008 #3
    ahhh thanks for answering both of my questions!

    good night!
     
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