Question 441687
 hoe many line segments are determined by the n vertices of an n-gon? of these, how many are diagnols?
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Each pair of vertices determines a line.
# of line segments determined = nC2 =  (n(n-1))/2
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# of sides + number of diagonals = (n(n-1))/2
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number of diagonals = (n(n-1))/2 - n
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Cheers,
Stan H.