proposition: Lemma factmod_mx_repr : mx_repr G (factmod_mx Umod).
proof: Proof. split=> [|x y Gx Gy /=]. by rewrite /factmod_mx repr_mx1 mulmx1 val_factmodK. by rewrite -in_factmodJ // -mulmxA -repr_mxM. 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)