I study Polygon Triangulation and have an execise.
Prove or disprove: The dual graph of the triangulation of a monotone polygon is always a chain, that is, any node in this graph has degree at most two.
It seems like the assumption that the dual graph of the triangulation of a monotone polygon is always a chain is false. But how to prove this.
Let's say if it was true, at least one edge of every triangle would be a part of the boundary of the polygon.
I don't have any idea how approach the proof. Please help me out.