proposition: Lemma sgr1 : sg 1 = 1 :> R.
proof: Proof. by rewrite gtr0_sg // ltr01. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)