Session 3, Part B:
Classifying Polygons (40 minutes)

In This Part: Properties of Polygons | Grouping Polygons | Polygon-Classification Game
More Venn Diagrams

 Polygons can be divided into groups according to certain properties. Concave polygons look like they are collapsed or have one or more angles dented in. Any polygon that has an angle measuring more than 180° is concave. These are concave polygons: These polygons are not concave:

 Regular polygons have sides that are all the same length and angles that are all the same size. These polygons are regular: The polygons below are not regular. Such polygons are referred to as irregular. Note 3 A polygon has line symmetry, or reflection symmetry, if you can fold it in half along a line so the two halves match exactly. The "folding line" is called the line of symmetry. These polygons have line symmetry. The lines of symmetry are shown as dashed lines. Notice that two of the polygons have more than one line of symmetry. These polygons do not have line symmetry:

 Session 3: Index | Notes | Solutions | Video