proposition: Lemma lower_dim : lower_dimP Point bet' a' b' c'.
proof: Proof. rewrite /lower_dimP /Col nbet_abc nbet_cab nbet_bca. by move=> [|[|]]. Qed.
imports: mathcomp.ssreflect.ssreflect mathcomp(ssrbool ssrfun ssrnat eqtype choice seq) mathcomp(fintype finset finfun bigop order) mathcomp(ssralg ssrnum path generic_quotient matrix mxalgebra) mathcomp(zmodp) GeoCoq.Meta_theory.Models.POF_to_Tarski GeoCoq.Meta_theory.Counter_models.Planar.independence