Theorem: IntermediateField.adjoin_toSubalgebra_of_isAlgebraic
File: Mathlib/FieldTheory/Adjoin.lean

tactic: let i := IsScalarTower.toAlgHom F E K
state_before: F : Type u_1
inst✝⁶ : Field F
E : Type u_2
inst✝⁵ : Field E
inst✝⁴ : Algebra F E
S : Set E
α : E
K : Type u_3
inst✝³ : Field K
inst✝² : Algebra F K
inst✝¹ : Algebra E K
inst✝ : IsScalarTower F E K
L : IntermediateField F K
halg : Algebra.IsAlgebraic F E ∨ Algebra.IsAlgebraic F ↥L
⊢ (adjoin E ↑L).toSubalgebra = Algebra.adjoin E ↑L
state_after: F : Type u_1
inst✝⁶ : Field F
E : Type u_2
inst✝⁵ : Field E
inst✝⁴ : Algebra F E
S : Set E
α : E
K : Type u_3
inst✝³ : Field K
inst✝² : Algebra F K
inst✝¹ : Algebra E K
inst✝ : IsScalarTower F E K
L : IntermediateField F K
halg : Algebra.IsAlgebraic F E ∨ Algebra.IsAlgebraic F ↥L
i : E →ₐ[F] K := IsScalarTower.toAlgHom F E K
⊢ (adjoin E ↑L).toSubalgebra = Algebra.adjoin E ↑L

tactic: let E' := i.fieldRange
state_before: F : Type u_1
inst✝⁶ : Field F
E : Type u_2
inst✝⁵ : Field E
inst✝⁴ : Algebra F E
S : Set E
α : E
K : Type u_3
inst✝³ : Field K
inst✝² : Algebra F K
inst✝¹ : Algebra E K
inst✝ : IsScalarTower F E K
L : IntermediateField F K
halg : Algebra.IsAlgebraic F E ∨ Algebra.IsAlgebraic F ↥L
i : E →ₐ[F] K := IsScalarTower.toAlgHom F E K
⊢ (adjoin E ↑L).toSubalgebra = Algebra.adjoin E ↑L
state_after: F : Type u_1
inst✝⁶ : Field F
E : Type u_2
inst✝⁵ : Field E
inst✝⁴ : Algebra F E
S : Set E
α : E
K : Type u_3
inst✝³ : Field K
inst✝² : Algebra F K
inst✝¹ : Algebra E K
inst✝ : IsScalarTower F E K
L : IntermediateField F K
halg : Algebra.IsAlgebraic F E ∨ Algebra.IsAlgebraic F ↥L
i : E →ₐ[F] K := IsScalarTower.toAlgHom F E K
E' : IntermediateField F K := i.fieldRange
⊢ (adjoin E ↑L).toSubalgebra = Algebra.adjoin E ↑L

tactic: let i' : E ≃ₐ[F] E' := AlgEquiv.ofInjectiveField i
state_before: F : Type u_1
inst✝⁶ : Field F
E : Type u_2
inst✝⁵ : Field E
inst✝⁴ : Algebra F E
S : Set E
α : E
K : Type u_3
inst✝³ : Field K
inst✝² : Algebra F K
inst✝¹ : Algebra E K
inst✝ : IsScalarTower F E K
L : IntermediateField F K
halg : Algebra.IsAlgebraic F E ∨ Algebra.IsAlgebraic F ↥L
i : E →ₐ[F] K := IsScalarTower.toAlgHom F E K
E' : IntermediateField F K := i.fieldRange
⊢ (adjoin E ↑L).toSubalgebra = Algebra.adjoin E ↑L
state_after: F : Type u_1
inst✝⁶ : Field F
E : Type u_2
inst✝⁵ : Field E
inst✝⁴ : Algebra F E
S : Set E
α : E
K : Type u_3
inst✝³ : Field K
inst✝² : Algebra F K
inst✝¹ : Algebra E K
inst✝ : IsScalarTower F E K
L : IntermediateField F K
halg : Algebra.IsAlgebraic F E ∨ Algebra.IsAlgebraic F ↥L
i : E →ₐ[F] K := IsScalarTower.toAlgHom F E K
E' : IntermediateField F K := i.fieldRange
i' : E ≃ₐ[F] ↥E' := AlgEquiv.ofInjectiveField i
⊢ (adjoin E ↑L).toSubalgebra = Algebra.adjoin E ↑L

tactic: have hi : algebraMap E K = (algebraMap E' K) ∘ i' := by ext x; rfl
state_before: F : Type u_1
inst✝⁶ : Field F
E : Type u_2
inst✝⁵ : Field E
inst✝⁴ : Algebra F E
S : Set E
α : E
K : Type u_3
inst✝³ : Field K
inst✝² : Algebra F K
inst✝¹ : Algebra E K
inst✝ : IsScalarTower F E K
L : IntermediateField F K
halg : Algebra.IsAlgebraic F E ∨ Algebra.IsAlgebraic F ↥L
i : E →ₐ[F] K := IsScalarTower.toAlgHom F E K
E' : IntermediateField F K := i.fieldRange
i' : E ≃ₐ[F] ↥E' := AlgEquiv.ofInjectiveField i
⊢ (adjoin E ↑L).toSubalgebra = Algebra.adjoin E ↑L
state_after: F : Type u_1
inst✝⁶ : Field F
E : Type u_2
inst✝⁵ : Field E
inst✝⁴ : Algebra F E
S : Set E
α : E
K : Type u_3
inst✝³ : Field K
inst✝² : Algebra F K
inst✝¹ : Algebra E K
inst✝ : IsScalarTower F E K
L : IntermediateField F K
halg : Algebra.IsAlgebraic F E ∨ Algebra.IsAlgebraic F ↥L
i : E →ₐ[F] K := IsScalarTower.toAlgHom F E K
E' : IntermediateField F K := i.fieldRange
i' : E ≃ₐ[F] ↥E' := AlgEquiv.ofInjectiveField i
hi : ⇑(algebraMap E K) = ⇑(algebraMap (↥E') K) ∘ ⇑i'
⊢ (adjoin E ↑L).toSubalgebra = Algebra.adjoin E ↑L

tactic: apply_fun _ using Subalgebra.restrictScalars_injective F
state_before: F : Type u_1
inst✝⁶ : Field F
E : Type u_2
inst✝⁵ : Field E
inst✝⁴ : Algebra F E
S : Set E
α : E
K : Type u_3
inst✝³ : Field K
inst✝² : Algebra F K
inst✝¹ : Algebra E K
inst✝ : IsScalarTower F E K
L : IntermediateField F K
halg : Algebra.IsAlgebraic F E ∨ Algebra.IsAlgebraic F ↥L
i : E →ₐ[F] K := IsScalarTower.toAlgHom F E K
E' : IntermediateField F K := i.fieldRange
i' : E ≃ₐ[F] ↥E' := AlgEquiv.ofInjectiveField i
hi : ⇑(algebraMap E K) = ⇑(algebraMap (↥E') K) ∘ ⇑i'
⊢ (adjoin E ↑L).toSubalgebra = Algebra.adjoin E ↑L
state_after: F : Type u_1
inst✝⁶ : Field F
E : Type u_2
inst✝⁵ : Field E
inst✝⁴ : Algebra F E
S : Set E
α : E
K : Type u_3
inst✝³ : Field K
inst✝² : Algebra F K
inst✝¹ : Algebra E K
inst✝ : IsScalarTower F E K
L : IntermediateField F K
halg : Algebra.IsAlgebraic F E ∨ Algebra.IsAlgebraic F ↥L
i : E →ₐ[F] K := IsScalarTower.toAlgHom F E K
E' : IntermediateField F K := i.fieldRange
i' : E ≃ₐ[F] ↥E' := AlgEquiv.ofInjectiveField i
hi : ⇑(algebraMap E K) = ⇑(algebraMap (↥E') K) ∘ ⇑i'
⊢ Subalgebra.restrictScalars F (adjoin E ↑L).toSubalgebra = Subalgebra.restrictScalars F (Algebra.adjoin E ↑L)

tactic: erw [← restrictScalars_toSubalgebra, restrictScalars_adjoin_of_algEquiv i' hi,
  Algebra.restrictScalars_adjoin_of_algEquiv i' hi, restrictScalars_adjoin,
  Algebra.restrictScalars_adjoin]
state_before: F : Type u_1
inst✝⁶ : Field F
E : Type u_2
inst✝⁵ : Field E
inst✝⁴ : Algebra F E
S : Set E
α : E
K : Type u_3
inst✝³ : Field K
inst✝² : Algebra F K
inst✝¹ : Algebra E K
inst✝ : IsScalarTower F E K
L : IntermediateField F K
halg : Algebra.IsAlgebraic F E ∨ Algebra.IsAlgebraic F ↥L
i : E →ₐ[F] K := IsScalarTower.toAlgHom F E K
E' : IntermediateField F K := i.fieldRange
i' : E ≃ₐ[F] ↥E' := AlgEquiv.ofInjectiveField i
hi : ⇑(algebraMap E K) = ⇑(algebraMap (↥E') K) ∘ ⇑i'
⊢ Subalgebra.restrictScalars F (adjoin E ↑L).toSubalgebra = Subalgebra.restrictScalars F (Algebra.adjoin E ↑L)
state_after: F : Type u_1
inst✝⁶ : Field F
E : Type u_2
inst✝⁵ : Field E
inst✝⁴ : Algebra F E
S : Set E
α : E
K : Type u_3
inst✝³ : Field K
inst✝² : Algebra F K
inst✝¹ : Algebra E K
inst✝ : IsScalarTower F E K
L : IntermediateField F K
halg : Algebra.IsAlgebraic F E ∨ Algebra.IsAlgebraic F ↥L
i : E →ₐ[F] K := IsScalarTower.toAlgHom F E K
E' : IntermediateField F K := i.fieldRange
i' : E ≃ₐ[F] ↥E' := AlgEquiv.ofInjectiveField i
hi : ⇑(algebraMap E K) = ⇑(algebraMap (↥E') K) ∘ ⇑i'
⊢ (adjoin F (↑E' ∪ ↑L)).toSubalgebra = Algebra.adjoin F (↑E'.toSubalgebra ∪ ↑L)

tactic: exact E'.sup_toSubalgebra_of_isAlgebraic L (halg.imp
  (fun (_ : Algebra.IsAlgebraic F E) ↦ i'.isAlgebraic) id)
state_before: F : Type u_1
inst✝⁶ : Field F
E : Type u_2
inst✝⁵ : Field E
inst✝⁴ : Algebra F E
S : Set E
α : E
K : Type u_3
inst✝³ : Field K
inst✝² : Algebra F K
inst✝¹ : Algebra E K
inst✝ : IsScalarTower F E K
L : IntermediateField F K
halg : Algebra.IsAlgebraic F E ∨ Algebra.IsAlgebraic F ↥L
i : E →ₐ[F] K := IsScalarTower.toAlgHom F E K
E' : IntermediateField F K := i.fieldRange
i' : E ≃ₐ[F] ↥E' := AlgEquiv.ofInjectiveField i
hi : ⇑(algebraMap E K) = ⇑(algebraMap (↥E') K) ∘ ⇑i'
⊢ (adjoin F (↑E' ∪ ↑L)).toSubalgebra = Algebra.adjoin F (↑E'.toSubalgebra ∪ ↑L)
state_after: no goals

tactic: ext x
state_before: F : Type u_1
inst✝⁶ : Field F
E : Type u_2
inst✝⁵ : Field E
inst✝⁴ : Algebra F E
S : Set E
α : E
K : Type u_3
inst✝³ : Field K
inst✝² : Algebra F K
inst✝¹ : Algebra E K
inst✝ : IsScalarTower F E K
L : IntermediateField F K
halg : Algebra.IsAlgebraic F E ∨ Algebra.IsAlgebraic F ↥L
i : E →ₐ[F] K := IsScalarTower.toAlgHom F E K
E' : IntermediateField F K := i.fieldRange
i' : E ≃ₐ[F] ↥E' := AlgEquiv.ofInjectiveField i
⊢ ⇑(algebraMap E K) = ⇑(algebraMap (↥E') K) ∘ ⇑i'
state_after: case h
F : Type u_1
inst✝⁶ : Field F
E : Type u_2
inst✝⁵ : Field E
inst✝⁴ : Algebra F E
S : Set E
α : E
K : Type u_3
inst✝³ : Field K
inst✝² : Algebra F K
inst✝¹ : Algebra E K
inst✝ : IsScalarTower F E K
L : IntermediateField F K
halg : Algebra.IsAlgebraic F E ∨ Algebra.IsAlgebraic F ↥L
i : E →ₐ[F] K := IsScalarTower.toAlgHom F E K
E' : IntermediateField F K := i.fieldRange
i' : E ≃ₐ[F] ↥E' := AlgEquiv.ofInjectiveField i
x : E
⊢ (algebraMap E K) x = (⇑(algebraMap (↥E') K) ∘ ⇑i') x

tactic: rfl
state_before: case h
F : Type u_1
inst✝⁶ : Field F
E : Type u_2
inst✝⁵ : Field E
inst✝⁴ : Algebra F E
S : Set E
α : E
K : Type u_3
inst✝³ : Field K
inst✝² : Algebra F K
inst✝¹ : Algebra E K
inst✝ : IsScalarTower F E K
L : IntermediateField F K
halg : Algebra.IsAlgebraic F E ∨ Algebra.IsAlgebraic F ↥L
i : E →ₐ[F] K := IsScalarTower.toAlgHom F E K
E' : IntermediateField F K := i.fieldRange
i' : E ≃ₐ[F] ↥E' := AlgEquiv.ofInjectiveField i
x : E
⊢ (algebraMap E K) x = (⇑(algebraMap (↥E') K) ∘ ⇑i') x
state_after: no goals