[b]Click the "▶" button. Observe the angles turned by the car at the corners. Drag the green points. [/b][br]1. What is a + b + c + d + e, the total angle sum turned by the car?[br]2. The points a, b, c, d, e are called the exterior angles of the convex pentagon ABCDE. [br] In general, what is the sum of all exterior angles of a convex polygon?[br]3. How would you modify the result if the pentagon ABCDE is NOT convex?

Anthony Or. Education Bureau, Hong Kong.