Review: Classifying Polygons

Use With Lesson 1-8

In geometry, a figure that lies in a plane is called a plane figure.

A polygon is a closed plane figure formed by three or more segments. Each segment intersects exactly two other segments at their endpoints. No two segments with a common endpoint are collinear. Each segment is called a side. Each endpoint of a side is a vertex.

A polygon

Not a polygon; not a closed figure

Not a polygon; two sides intersect between endpoints.

To name a polygon, start at any vertex and list the vertices consecutively in a clockwise or counterclockwise direction.

Example 1

Name the polygon. Then identify its sides and angles.

Two names for this polygon are DHKMGB and MKHDBG.

sides: D H ¯ , H K ¯ , K M ¯ , M G ¯ , G B ¯ , B B ¯ d h bar , comma , h k bar , comma , k m bar , comma , m g bar , comma , g b bar , comma , b b bar

angles: ∠ D , ∠ H , ∠ K , ∠ M , ∠ G , ∠ B angle d comma angle h comma angle k comma angle m comma angle g comma angle b

You can classify a polygon by its number of sides. The tables below show the names of some common polygons.

Table of Contents