proposition: Lemma braid_trans : transitive braidcongr.
proof: Proof. Proof using. have:= braid_equiv; rewrite equivalence_relP => [] [Hrefl Hltr]. by move=> i j k => /Hltr <-. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(fingroup perm morphism presentation) mathcomp(ssralg poly ssrint) permcomp tools permuted combclass congr