Interior and exterior angles in regular polygons
Make the polygon have 8 sides. (n=8) If you added up all 8 interior angles, what would the total sum be?
Now try the formula: (n-2) * 180 n=8, so (8-2)*180 What value do you get?
Look back at the figure. What would the sum of all 8 exterior angles be?
Now change n to any other value. Check the interior angle sum again. Does the formula still work? What would the sum of all exterior angles be now?