proposition: Lemma mx_iso_sym U V : mx_iso U V -> mx_iso V U.
proof: Proof. case=> f injf homUf defV; exists (invmx f); first by rewrite unitmx_inv. by rewrite dom_hom_invmx // -defV submxMr. by rewrite -[U](mulmxK injf); apply: eqmxMr (eqmx_sym _). Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq path) mathcomp(div choice fintype tuple finfun bigop prime) mathcomp(ssralg poly polydiv finset fingroup morphism) mathcomp(perm automorphism quotient finalg action zmodp) mathcomp(commutator cyclic center pgroup matrix mxalgebra) mathcomp(mxpoly)