Part 1
I present three cases of tubes, that, relate to numerical 13.
First my own geometric discovery { cosmic I believe }:
1} a tube defined by three triangles, ergo,:
..> three sets of six lines-of-relationship{ LoR's }, and three sets of nodal event points = nine nodal event points,
...> six lines of LoR's connecting those 9 nodal events
This above set defines the minimal set needed to define tube via,
..> triangular enclosure on both ends, and,
...> a mid-girth { waist/around } triangle.
Here is a couple of graphics to aid in visualization of the above.
..> a triangular bifrustum polyhedron https://en.wikipedia.org/wiki/Triangular_bifrustum
and,
In geometry, the triangular bifrustum is the second in an infinite series of bifrustum polyhedra. It has 6 trapezoid and 2 triangle faces. It may also be called the truncated triangular bipyramid; however, that term is ambiguous, as it may also refer to polyhedra formed by truncating all five vertices of a triangular bipyramid.
This polyhedron c...


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