Fig. 2: Co-circular and near-degenerate point configurations.
From: Shape graphs and the instantaneous inference of tactical positions in soccer
a For four points on an otherwise empty circle with center c, either diagonal can be in the Delaunay triangulation. b After translating \(r\to {r}^{{\prime} }\), only pq is a Delaunay edge, because the two circles defined by p, q and one of \({r}^{{\prime} },s\) do not enclose the remaining point, whereas those defined by \({r}^{{\prime} },s\) and one of p, q do. The two pairs of circumcenters are necessarily separated by the same angle α.
