proposition: Lemma mulr_Nsign_norm x : (-1) ^+ (0 < x)%R * `|x| = - x.
proof: Proof. by rewrite real_mulr_Nsign_norm. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)