Exterior Angles of Polygons (Updated with Negative Angles)

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 by the car? 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. Is the result still true if the pentagon ABCDE is NOT convex? Anthony Or. GeoGebra Institute of Hong Kong.