proposition: Lemma quo_mx_repr : mx_repr (G / H)%g (quo_mx krH nHG).
proof: Proof. split=> [|Hx Hy]; first by rewrite /quo_mx repr_coset1 repr_mx1. case/morphimP=> x Nx Gx ->{Hx}; case/morphimP=> y Ny Gy ->{Hy}. by rewrite -morphM // !quo_mx_coset ?groupM ?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)