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Homework Help: Quick math question

  1. Dec 4, 2007 #1
    d=n^2 - 3n / 2

    where d = number of diagonals
    and n = the number of sides of the polygon.

    A polygon has 119 diagonals, how many sides does it have?

    119 = n^2 - 3n / 2

    I am not sure how to do this? can someone please help?

    sorry this isn't physics related
  2. jcsd
  3. Dec 5, 2007 #2
    An n-sided polygon has this many diagonals:


    Solve for [tex]n[/tex].
  4. Dec 5, 2007 #3


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    Quadratic Formula
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