proposition: Lemma abszEsg m : (`|m|%:Z = sgz m * m)%R.
proof: Proof. by rewrite -sgrz -normrEsg. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)