On Mon, Nov 16, 2020 at 11:29 AM James Propp <jamespropp@gmail.com> wrote:
On Mon, Nov 16, 2020 at 1:14 PM George Hart <george@georgehart.com> wrote:
Dan,
1. By the product of polygons P1 and P2, I just mean the Cartesian product: {p1 + p2 | p1 \in P1 && p2 \in P2}
George, I think you meant "Minkowski sum", not "Cartesian product".
He means the cartesian product of the polygon graphs, and you can assign coordinates to the product graph using the Minkowski sum. It's a terrible shame that the term "Cartesian product" of graphs was used for a construction that is not the categorical product of graphs. I far prefer the term "box product", because the box product of two edges forms a square, whereas the categorical product of two edges forms an x. -- Mike Stay - metaweta@gmail.com http://math.ucr.edu/~mike https://reperiendi.wordpress.com