Octagon - GCSE Maths Definition

An octagon is a polygon (2D shape with straight sides) with eight sides, and eight angles. In a regular octagon, all eight sides will be of equal length, and all eight angles will be equal. The exterior angle of a regular octagon can be found by dividing 360° by 8, so is 45°. Therefore, the interior angle of a regular octagon is 180° - 45° = 135°, and the interior angle sum is 135° x 8 = 1080°. In GCSE Mathematics, an octagon may feature in geometric problems, where finding unknown side lengths, angles, perimeters and/or areas is required.