proposition: Lemma isog_der (aT rT : finGroupType) n (G : {group aT}) (H : {group rT}) : G \isog H -> G^`(n) \isog H^`(n).
proof: Proof. exact: gFisog. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat fintype) mathcomp(bigop finset binomial fingroup morphism) mathcomp(automorphism quotient gfunctor)