Ans: Polygon is one of the most used geometrical shapes. A polygon with 8 sides is called an octagon. If the length of the sides of the octagon is equal, it is a regular octagon. The major properties of a regular octagon are-All the sides of a regular octagon are equal in length. A regular octagon has 8 equal interior angles and 8 equal exterior angles.Each interior angle is 45° and the sum of the interior angles is (45° × 8) = 360°.Each exterior angle is 135° and the sum of the exterior angles is (135° × 8) = 1080°.A regular octagon has a total of 20 diagonals.