A Polygon is a closed figure made up of line segments (not curves) in a two-dimensional plane. polygon can be defined as a flat or plane, two-dimensional closed shape bounded with straight sides. It does not have curved sides. The sides of a polygon are also called its edges. The points where two sides meet are the vertices (or corners) of a polygon.Polygon is the combination of two words, i.e. poly (means many) and gon (means sides).

Qu'est-ce qu'un polygone ? | MOMES

Types of Polygon

Depending on the sides and angles, the polygons are classified into different types, namely:

  • Regular Polygon - Polygons that have equal sides and angles are regular polygons. 
  • Irregular Polygon - Polygons with unequal sides and angles are irregular polygons.
  • Convex Polygon - A convex polygon is a polygon with all interior angles less than 180°.
  • Concave polygon - A concave polygon is a polygon with at least one interior angle greater than 180°.

Simple and Complex Polygon:

Simple Polygon – A simple polygon has only one boundary. The sides of a simple polygon do not intersect.

Complex Polygon – Complex polygon is a polygon whose sides cross over each other one or more times.

Sum of Angles of a Polygon : Sum of the interior angles of a polygon with n sides = (n – 2) × 180°

Sum of the exterior angles of polygons = 360°

Angles in Regular Polygon

In a regular polygon, all its

  • sides are equal
  • interior angles are equal
  • exterior angles are equal

Interior Angle: 

Sum of the interior angles of a polygon with n sides = (n – 2) × 180°

So, each interior angles =  (n – 2) × 180n 

Exterior Angle:

Sum of the exterior angles of polygons = 360°

So, each exterior angle = 360°n 

Sum of Interior Angle and Exterior Angle:

Whether the polygon is regular or irregular, at each vertex of the polygon sum of an interior angle and exterior angle is 180°.


The properties of polygons are based on their sides and angles. 

  • The sum of all the interior angles of an n-sided polygon is (n – 2) × 180°.
  • The number of diagonals in a polygon with n sides = n(n – 3)/2
  • The number of triangles formed by joining the diagonals from one corner of a polygon = n – 2
  • The measure of each interior angle of n-sided regular polygon = [(n – 2) × 180°]/n
  • The measure of each exterior angle of an n-sided regular polygon = 360°/n