Exterior angles are easy to define for convex polygons. They also lie outside the polygon, making it intuitive as to why they are called "exterior". But I'm a bit confused when we talk about exterior angles in concave polygons.
Let's say a 7 sided polygon has only one reflex interior angle (thus, making it concave). How is the exterior angle at the vertex containing the reflex angle defined? Because if one extends one of the sides of the polygon at that vertex, it enters the polygon. So the angle is no longer external? So not exterior? I'm really confused here. Any help?