A octagon is a polygon with 8 sides and 8 vertices.
A regular octagon is a polygon with 8 equal sides and angles.
Angles of the Octagon
The sum of interior angles of an octagon = (8 − 2) · 180° = 1,080°
The value of an interior angle of a regular octagon is: 1,080º : 8 = 135º
The central angle of a regular octagon measures: 360º : 8 = 45º
Diagonals of the Octagon
The number of diagonals in a regular octagon = 8 · (8 − 3) : 2 = 20
Perimeter of a Regular Octagon
Perimeter = 8 · l
Area of a Regular Octagon