An icosagon is a polygon with 20 sides and 20 vertices.
A regular icosagon is a polygon with 20 equal sides and angles.
Angles of the Icosagon
The sum of interior angles of a icosagon = (20 − 2) · 180° = 3,240°
The value of an interior angle of a regular icosagon is: 3,240º : 20 = 162º
The central angle of a regular icosagon measures: 360º : 20 = 18º
Diagonals of the Icosagon
The number of diagonals in a regular icosagon = 20 · (20 − 3) : 2 = 170
Perimeter of a Regular Icosagon
Perimeter = 20 · l
Area of a Regular Icosagon