Ask Dr. Math
Dr. Math Home ||
Middle School ||
High School ||
Dr. Math FAQ
- Polygon Diagonals
- The number of diagonals in a polygon = n(n-3)/2, where
n is the number of polygon sides.
- For a convex n-sided polygon, there are n vertices, and
from each vertex you can draw n-3 diagonals, so the total
number of diagonals that can be drawn is n(n-3). However,
this would mean that each diagonal would be drawn twice,
(to and from each vertex), so the expression must be
divided by 2.
- For more discussion, see the Dr. Math archives:
- Counting Diagonals
- How many diagonals can be drawn for a polygon with n sides?
- Diagonals of Polygons
- How many diagonals does a polygon with n sides have?
Middle School Triangles/Polygons
High School Triangles/Polygons
Index of Selected Answers to Common Questions
© 1994-2013 Drexel University. All rights reserved.
Home || The Math Library || Quick Reference || Search || Help
The Math Forum is a research and educational enterprise of the Drexel University School of Education.