SOLUTION: How many diagonal lines are there in a 25-sided polygon? ... How do I come up with this?

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Question 338359: How many diagonal lines are there in a 25-sided polygon? ... How do I come up with this?
Answer by edjones(8007) About Me  (Show Source):
You can put this solution on YOUR website!
n(n-3)/2 Number of diagonals in any convex polygon. n=number of sides.
25(25-3)/2
=25*22/2
=25*11
=275
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Ed