Who can prove that the sum of exterior angles of n-shape is 360 degrees pai314

Who can prove that the sum of exterior angles of n-shape is 360 degrees pai314

The sum of the inner angles of a polygon is (n-2) * 180 (n is the number of sides), and because each side is a flat angle, the total angle degree is n * 180
(n-2)*180-n*180=2*180=360