proposition: Lemma sgz_ge0 x : (sgz x >= 0) = (x >= 0).
proof: Proof. by case: sgzP. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)