Q&A #3829

Diagonals of polygons

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From: Jim and Carolyn (for Teacher2Teacher Service)
Date: May 01, 2000 at 16:37:11
Subject: Re: Diagonals of polygons

The formula to find the number of diagonals d in terms of the number of sides n is: d = (n(n - 3))/2. For example, in a pentagon the number of sides n is 5, so d = 5(5 - 3)/2 = 5. To understand the formula pick a vertex on a pentagon. Notice from that vertex you can draw exactly 2 diagonals, thus the n - 3 in the formula. Repeat this at each vertex which would make it appear to be 10 diagonals. However, each diagonal would have been drawn twice. (So divide by 2.) -Jim and Carolyn, for the Teacher2Teacher service

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