proposition: Lemma der_norm n G : G \subset 'N(G^`(n)).
proof: Proof. by rewrite char_norm ?der_char. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat fintype) mathcomp(bigop finset binomial fingroup morphism) mathcomp(automorphism quotient gfunctor)