what of a triangle has three line segments that intersect only at their endpoints
There are 28 lines segments that both have their endpoints located at the vertices of a given cube.
Some segments with both endpoints on a circle are not diameters.
12 of then but if they are joined together in the form of a 6 sided hexagon then 6 endpoints are needed.
That would be a polygon.
what of a triangle has three line segments that intersect only at their endpoints
4
Segments.
No. Line segments end at the endpoints.
All line segments have exactly two endpoints.
A polygon.
triangel
A triangle
There are 28 lines segments that both have their endpoints located at the vertices of a given cube.
Convex
polygons
figure