proposition: Lemma unitmx_inv A : (invmx A \in unitmx) = (A \in unitmx).
proof: Proof. by rewrite !unitmxE det_inv unitrV. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype finfun bigop finset fingroup perm order) mathcomp(div prime binomial ssralg countalg finalg zmodp)