Polygons

• polygons
• types of polygons
  • simple or complex
  • convex or concave
  • equilateral
  • equiangular
  • regular or irregular
• names of polygons (with worksheets)

Polygon

A polygon is a closed shape that has three or more sides. Each side is a line segment. The line segments form the sides of the polygon.

The following are examples of polygons:

The following figures are not polygons:

Types of Polygons

Simple Polygons or Complex Polygons

The sides of a simple polygon do not intersect. In a simple polygon, the line segments meet in pairs to form the vertices. Usually the word "simple" is omitted and the word "polygon" is used to mean "simple polygon".

A complex polygon has intersecting sides.

Convex Polygons or Concave Polygons

A convex polygon has all angles less than 180º.
A concave polygon has at least one angle greater than 180º. (memory tool: concave has a "cave" in it)

Equilateral Polygon

An equilateral polygon is a polygon which has all sides of the same length. A rhombus is an example of an equilateral polygon.

Equiangular Polygon

An equiangular polygon is a polygon whose interior angles are equal. A rectangle is an example of an equiangular polygon

Regular Polygons or Irregular Polygons

A regular polygon is a polygon with equal sides and equal angles otherwise it is an irregular polygon. A regular polygon is both equilateral and equiangular.

Naming Polygons

Some polygons have special names, depending on the number of sides they have.

Number of sides	Name of polygon
3	Triangle
4	Quadrilateral
5	Pentagon
6	Hexagon
7	Heptagon
8	Octagon
9	Nonagon
10	Decagon
11	Hendecagon
12	Dodecagon

For polygons with more sides, it is easier and quite common to use a number to indicate the number of sides. For eg. 15-gon or 23-gon.

Worksheets

Practise the names of polygons with the following worksheets

Names of Polygons - Give the number of sides

Names of Polygons - Give the names of polygons

The following video will show you how to define a polygon, how to distinguish between concave and convex polygons, how to name polygons.

The following video explains what are polygons, defines regular and irregular polygons and their features

The following video gives some examples of classifying polygons. Convex Hexagon, Concave Octagon, Covex Equilateral Nonagon.

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