We know the sum of exterior angles for a polygon is 360. 3 Solve the problem using the information you have already gathered. Exterior Angles Theorems Angles Worksheet They are Supplementary Angles. . Whenever you get to solve such problems you need to draw the diagram and need to know that the sum of all the interior angles in ant of the polygon is 180n-2 where n is the number of sides present in the polygon and then solve by this method. Let us justify our result. This is because if we join the exterior angles we will form a complete circle which represents 360. The sum of exterior angles is 360 The exterior angle is 360 5 72 The interior and exterior angles add up to 180 The interior angle is 180 - 72 108 Method two. Finding an exterior angle given an interior angle for an irregular polygon An irregular octagon has one interior angle of size 130ยบ. What is the formula for the sum of exterior angles. Ther