proposition: Lemma BRinv_mon a b: inc a BRps -> inc b BRps -> (\1r /r a <=r \1r /r b <-> b <=r a).
proof: Proof. move => pa pb; move: (BRps_sBR pa)(BRps_sBR pb) => ar br. move: (BRdiv_Mlelege0 RS1 pa RS1 pb); rewrite BRprod_1l // BRprod_1r //. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)