proposition: Lemma eltr_braid i : i.+1 < n0 -> 's_i * 's_i.+1 * 's_i = 's_i.+1 * 's_i * 's_i.+1.
proof: Proof. Proof using. move=> Hi. apply: tperm_braid; rewrite /eq_op /=. - by rewrite inord1i // inordi // !trivSimpl. - by rewrite inordi // inordi1 // !trivSimpl. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(fingroup perm morphism presentation) mathcomp(ssralg poly ssrint) permcomp tools permuted combclass congr