They form a vertex of the polygon.
The vertex is a point of polygon or polyhedra that is formed by 2 lines or 3 edges on a polyhedron.
Two triangles can be formed by the diagonals of one vertex of a four-sided polygon.
Vertex, I believe.
On a protractor and at each corner (vertex) of the polygon.
A vertex of a polygon is where 2 sides meet
Each point is called a vertex.