Re: [math-fun] Number of ways to pick 4 points from an m X n grid?

At least it agrees that I was right that squares and rectangles would give the same answer, and that (although I didn't say it here) circles and ellipses would, and that equilateral and isosceles triangles would. But apparently *all* triangular boundaries have the same answer? That's not obvious to me.

Affine transformations preserve ratios between areas.