Polygons

A polygon is a closed figure where the sides are all line segments. Each side must intersect exactly two others sides but only at their endpoints. The sides must be noncollinear and have a common endpoint.

A polygon is usually named after how many sides it has, a polygon with n-sides is called a n-gon. E.g. the building which houses United States Department of Defense is called pentagon since it has 5 sides.

Sides                  Polygon

3                           triangle

4                           quadrilateral

5                           pentagon

6                           hexagon

7                           heptagon

9                           nonagon

10                        decagon

A regular polygon is a polygon in which all sides are congruent and all the angles are congruent.

Video lesson

Determine whether the figures are polygons or not