Decagon Polygon: Definition, Types and properties

A decagon is defined as a polygon with ten sides. The word “deca” itself means “ten”. A decagon has 10 sides and 10 internal angles. It has ten vertices as well. Decagons may be irregular or regular.

Properties of Decagon

  • Each angle in a regular decagon is equal to 144°.
  • A regular decagon is one that has its 10 sides of equal length and 10 angles of equal measure.
  • All sides are the same length (congruent) and all interior angles are the same size i.e congruent in case of regular decagon.
  • Sum of all angles = 1440
  • Number of triangles created by drawing the diagonals from a given vertex=8
  • Straight sides, interior angle sum of 1440 degrees and exterior angle sum of 180 degrees, ten sides, flat, divides a plane into an inside and an outside.


Regular Decagons

A regular decagon is referred as a decagon that has all 10 sides equal in length and has all 10 interior angles equal in measure. To find the measure of the central angle of a regular decagon, make a circle in the middle. A circle is 360 degrees around. Divide that by ten angles. 3600 / 10 = 360. So, the measure of the central angle of a regular decagon is 36 degrees.

Irregular Decagons

Irregular decagons are those which have unequal sides and unequal angles. Few sides or angles may be same, but all of them are not.