Sum of Exterior Angles of Polygons

Click the "▶" button. Observe the angles turned by the car at the corners. Drag the green points. Check the "Show Measurement" box to see the measurements of the angles.
1. What is a + b + c + d + e, the total angles turned? 2. a, b, c, d, e are called the exterior angles of the convex pentagon ABCDE. In general, what is the sum of all exterior angles of a convex polygon? 3. How would you modify the result if the pentagon ABCDE is NOT convex? Anthony Or. Education Bureau, Hong Kong.