proposition: Lemma subRR x : x - x == 0.
proof: Proof. exact: (Real.add_opposite_right R). Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div order) mathcomp(ssralg ssrnum ssrint rat intdiv) Coq(Morphisms Setoid) fourcolor(real realsyntax)