How To: Find the interior angle sum of a polygon

In this tutorial the instructor shows a method to compute the interior angle sum of a polygon. He gives us the formula for the interior angle sum of a convex polygon as (n-2) * 180 where n is the number of sides of the polygon. He goes and take a 6 sided polygon as an example and does the math by substituting the value of 'n' in the equation and arrives at the result. This video clearly gives the formula and demonstrates with an example of how to calculate the sum of interior angles of a polygon.