proposition: Fact hsgp x : 0 < q.[x] -> sgr p.[x] = sp'c.
proof: Proof. by rewrite -sgr_cp0 sgp => /eqP->; rewrite mulr1. Qed.
imports: mathcomp.ssreflect.ssreflect mathcomp(ssrfun ssrbool eqtype ssrnat seq choice fintype) mathcomp(bigop order ssralg poly polydiv ssrnum zmodp) mathcomp(polyorder path interval ssrint)