http://www.ck12.org Chapter 1. Basics of Geometry
A convex polygon does not share this property.
Diagonalsare line segments that connect the vertices of a convex polygon that are not sides.
The red lines are all diagonals. This pentagon has 5 diagonals.
Whether a polygon is convex or concave, it can always be named by the number of sides. See the chart below.
TABLE1.1:
Polygon Name Number of Sides Number of Diagonals Convex Example
Triangle 3 0Quadrilateral 4 2Pentagon 5 5