Question 4305
 No matter what size of polygons (convex or concave).
 the sum of the measure of the exterior angles is always 2pi.

 Proof: For any n polygons(n > 3),since we can divide it
        as (n-2) triangles. So,the sum all its interior angles
        is (n-2)pi. Since an interior angle + its corresponding exterior
        angle = pi. We see that the sum of all exterior angles
        = n*pi - (n-2)pi = 2 pi

 Kenny