proposition: Lemma subcent1_sub x G : 'C_G[x] \subset G.
proof: Proof. exact: subsetIl. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq div) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient action gproduct gfunctor) mathcomp(cyclic)