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Algebra question - quick visual

  1. Oct 26, 2009 #1
    It's a physics question but I need help solving for the radius in the picture bellow
    I need to solve for r so i can finish my physics question off


    my work so far

    (r-y)^2 + L^2 = r^2

    r^2 - (2*r*y) + y^2 + L^2 = r^2

    I'm not to sure how to solve this from here
    algebraically, for r

    Attached Files:

  2. jcsd
  3. Oct 26, 2009 #2


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    Homework Helper

    subtract r^2 from both sides, then divide everything by -2y
  4. Oct 26, 2009 #3
    bah I didn't see how friggen simple it was
    I thought I had to pull out some hardcore mathematics

    If I had continued and just removed r^2 in the first place instead of asking what to do

    2ry = y^2 + L^2
    r = (y^2)+(L^2) / 2y

    cheers big ears
  5. Oct 27, 2009 #4
    Carefull now. Remember that the 2y is dividing the entire right-hand side, not just the L^2
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