proposition: Lemma eqR_trans x y z : x == y -> y == z -> x == z.
proof: Proof. by move=> [lexy leyx] [/(leR_trans lexy)lexz /leR_trans/(_ leyx)]. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div order) mathcomp(ssralg ssrnum ssrint rat intdiv) Coq(Morphisms Setoid) fourcolor(real realsyntax)