No Matter How Many Sides, the Exterior Angle Sum Is Always 360°
Change the number of sides with the slider. The interior angle sum keeps growing as the number of sides increases, but the exterior angle sum stays exactly 360° whether it's a triangle or a 12-sided polygon.
Exterior angle is the angle between a side extended past a vertex and the next side. At every vertex of a polygon, "interior angle + exterior angle = 180°" always holds. Imagine walking once all the way around the shape's perimeter — add up the angle you turn at each vertex (the exterior angle), and it comes out to exactly one full turn (360°).