There are a total of 20 diagonals in a regular octagon. An Interior Angle is an angle inside a shape. 11 Angle Sum Of Any Polygon Maths Tutorials Youtube Math Tutorials Math For Kids Math Activities Regular polygons are always convex. . The sum of the angles of an octagon is 1080. What is the Sum of all Interior Angles of a Pentagon. Since the sum of the angles of the triangles is equal to 180 degrees. Hence the sum of all exterior angles is 45 x 8 360 degrees. One or more interior angles greater than 180. The sum of the interior angles of a regular octagon is 1080 degrees which makes each angle equal to 135 degrees in measure. Make sure each triangle here adds up to 180 and check that the pentagons interior angles. An octagon has eight sides and thus it has eight interior angles. The sum of the interior angles of a regular hexagon is 6 times 120 which is equal to 720. All the internal ang