Section FieldExtTheory.
Variables (F0 : fieldType) (L : fieldExtType F0).
Implicit Types (U V M : {vspace L}) (E F K : {subfield L}).
Canonical prodv_comoid := Monoid.ComLaw prodvC.
Canonical aimg_aspace rT f E := ASpace (@aimg_is_aspace rT f E).

Lemma Fadjoin_idP {K x} : reflect (<<K; x>>%VS = K) (x \in K).