proposition: Lemma sqre_ge0 x : 0 <= x ^+ 2.
proof: Proof. by case: x => [x||]; rewrite /= ?mulyy ?mulNyNy ?le0y//; apply: sqr_ge0. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap) mathcomp(mathcomp_extra) signed