-- Module: Mathlib.FieldTheory.Galois.Profinite
Goal:
k : Type u_3
K : Type u_4
inst : Field k
inst_1 : Field K
inst_2 : Algebra k K
g :
  (↑((limit (J := (FiniteGaloisIntermediateField k K)ᵒᵖ) (asProfiniteGaloisGroupFunctor k K)).toProfinite.toTop (P :=
        fun (X : TopCat.{u_4}) ↦ TotallyDisconnectedSpace.{u_4} (↑X : Type u_4))) :
    Type u_4)
L : IntermediateField k K
finiteDimensional : FiniteDimensional.{u_3, u_4} k ↥L
isGalois : IsGalois.{u_3, u_4} k ↥L
x :
  ↥{ toIntermediateField := L, finiteDimensional := finiteDimensional, isGalois := isGalois :
        FiniteGaloisIntermediateField k K }.toIntermediateField
L' : IntermediateField k K
finiteDimensional_1 : FiniteDimensional.{u_3, u_4} k ↥L'
isGalois_1 : IsGalois.{u_3, u_4} k ↥L'
h :
  { toIntermediateField := L, finiteDimensional := finiteDimensional, isGalois := isGalois :
      FiniteGaloisIntermediateField k K } ≤
    { toIntermediateField := L', finiteDimensional := finiteDimensional_1, isGalois := isGalois_1 }
this_1 : Algebra ↥L ↥L' := (Subsemiring.inclusion h).toAlgebra
this : IsScalarTower.{u_3, u_4, u_4} k ↥L ↥L' := ⋯
⊢ Eq (α := K)
    ((algebraMap (↥L') K : (a : ↥L') → K)
        ((((proj
                      { toIntermediateField := L', finiteDimensional := finiteDimensional_1, isGalois := isGalois_1 :
                        FiniteGaloisIntermediateField k K } :
                    (a : (↑(limit (asProfiniteGaloisGroupFunctor k K)).toProfinite.toTop : Type u_4)) →
                      Gal(↥{ toIntermediateField := L', finiteDimensional := finiteDimensional_1,
                              isGalois := isGalois_1 }.toIntermediateField/k))
                  g :
                Gal(↥{ toIntermediateField := L', finiteDimensional := finiteDimensional_1, isGalois := isGalois_1 :
                        FiniteGaloisIntermediateField k K }.toIntermediateField/k)) :
              (a :
                  ↥{ toIntermediateField := L', finiteDimensional := finiteDimensional_1,
                        isGalois := isGalois_1 }.toIntermediateField) →
                ↥{ toIntermediateField := L', finiteDimensional := finiteDimensional_1,
                      isGalois := isGalois_1 }.toIntermediateField)
            ((algebraMap ↥L
                  ↥{ toIntermediateField := L', finiteDimensional := finiteDimensional_1, isGalois := isGalois_1 :
                        FiniteGaloisIntermediateField k K }.toIntermediateField :
                (a : ↥L) →
                  ↥{ toIntermediateField := L', finiteDimensional := finiteDimensional_1,
                        isGalois := isGalois_1 }.toIntermediateField)
              x) :
          ↥{ toIntermediateField := L', finiteDimensional := finiteDimensional_1, isGalois := isGalois_1 :
                FiniteGaloisIntermediateField k K }.toIntermediateField) :
      K)
    ((↑((((proj
                      { toIntermediateField := L', finiteDimensional := finiteDimensional_1, isGalois := isGalois_1 :
                        FiniteGaloisIntermediateField k K } :
                    (a : (↑(limit (asProfiniteGaloisGroupFunctor k K)).toProfinite.toTop : Type u_4)) →
                      Gal(↥{ toIntermediateField := L', finiteDimensional := finiteDimensional_1,
                              isGalois := isGalois_1 }.toIntermediateField/k))
                  g :
                Gal(↥{ toIntermediateField := L', finiteDimensional := finiteDimensional_1, isGalois := isGalois_1 :
                        FiniteGaloisIntermediateField k K }.toIntermediateField/k)) :
              (a :
                  ↥{ toIntermediateField := L', finiteDimensional := finiteDimensional_1,
                        isGalois := isGalois_1 }.toIntermediateField) →
                ↥{ toIntermediateField := L', finiteDimensional := finiteDimensional_1,
                      isGalois := isGalois_1 }.toIntermediateField)
            (Subtype.mk (p := fun (x : K) ↦
              x ∈
                { toIntermediateField := L', finiteDimensional := finiteDimensional_1, isGalois := isGalois_1 :
                    FiniteGaloisIntermediateField k K }.toIntermediateField)
              (↑x : K) ⋯)) :
        K) :
      K)

Tactic:
rfl