proposition: Lemma limg_gal E (x : gal_of E) : (x @: E)%VS = E.
proof: Proof. by have:= gal_AEnd x; rewrite inE subfield_closed => /andP[_ /eqP]. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq div) mathcomp(choice fintype tuple finfun bigop ssralg poly) mathcomp(polydiv finset fingroup morphism quotient perm) mathcomp(action zmodp cyclic matrix mxalgebra vector) mathcomp(falgebra fieldext separable)