Module: Mathlib.NumberTheory.NumberField.Discriminant.Different

Goal state before:
pp: case refine_1
K : Type u_1
𝒪 : Type u_2
inst✝⁷ : Field K
inst✝⁶ : NumberField K
inst✝⁵ : CommRing 𝒪
inst✝⁴ : Algebra 𝒪 K
inst✝³ : IsFractionRing 𝒪 K
inst✝² : IsDedekindDomain 𝒪
inst✝¹ : CharZero 𝒪
inst✝ : Module.Finite ℤ 𝒪
this✝ :
  (↥↑1 ⧸ Submodule.comap (↑1).subtype ↑↑(differentIdeal ℤ 𝒪)) ≃ₗ[𝒪]
    ↥↑(↑(differentIdeal ℤ 𝒪))⁻¹ ⧸ Submodule.comap (↑(↑(differentIdeal ℤ 𝒪))⁻¹).subtype ↑1
this :
  Nat.card (↥↑1 ⧸ Submodule.comap (↑1).subtype ↑↑(differentIdeal ℤ 𝒪)) =
    Nat.card (↥↑(↑(differentIdeal ℤ 𝒪))⁻¹ ⧸ Submodule.comap (↑(↑(differentIdeal ℤ 𝒪))⁻¹).subtype ↑1)
b : Basis (Free.ChooseBasisIndex ℤ (𝓞 K)) ℚ K := integralBasis K
b' : Basis (Free.ChooseBasisIndex ℤ (𝓞 K)) ℚ K := (Algebra.traceForm ℚ K).dualBasis ⋯ b
hb : Submodule.span ℤ (Set.range ⇑b) = Submodule.restrictScalars ℤ 1
⊢ ↑1 ≤ ↑(FractionalIdeal.dual ℤ ℚ 1)

pp: K : Type u_1
𝒪 : Type u_2
inst✝⁷ : Field K
inst✝⁶ : NumberField K
inst✝⁵ : CommRing 𝒪
inst✝⁴ : Algebra 𝒪 K
inst✝³ : IsFractionRing 𝒪 K
inst✝² : IsDedekindDomain 𝒪
inst✝¹ : CharZero 𝒪
inst✝ : Module.Finite ℤ 𝒪
this✝ :
  (↥↑1 ⧸ Submodule.comap (↑1).subtype ↑↑(differentIdeal ℤ 𝒪)) ≃ₗ[𝒪]
    ↥↑(↑(differentIdeal ℤ 𝒪))⁻¹ ⧸ Submodule.comap (↑(↑(differentIdeal ℤ 𝒪))⁻¹).subtype ↑1
this :
  Nat.card (↥↑1 ⧸ Submodule.comap (↑1).subtype ↑↑(differentIdeal ℤ 𝒪)) =
    Nat.card (↥↑(↑(differentIdeal ℤ 𝒪))⁻¹ ⧸ Submodule.comap (↑(↑(differentIdeal ℤ 𝒪))⁻¹).subtype ↑1)
b : Basis (Free.ChooseBasisIndex ℤ (𝓞 K)) ℚ K := ⋯
b' : Basis (Free.ChooseBasisIndex ℤ (𝓞 K)) ℚ K := ⋯
hb : Submodule.span ℤ (Set.range ⇑b) = Submodule.restrictScalars ℤ 1
⊢ Submonoid 𝒪

Tactic:
]

Goal state after:
case refine_1
K : Type u_1
𝒪 : Type u_2
inst✝⁷ : Field K
inst✝⁶ : NumberField K
inst✝⁵ : CommRing 𝒪
inst✝⁴ : Algebra 𝒪 K
inst✝³ : IsFractionRing 𝒪 K
inst✝² : IsDedekindDomain 𝒪
inst✝¹ : CharZero 𝒪
inst✝ : Module.Finite ℤ 𝒪
this✝ :
  (↥↑1 ⧸ Submodule.comap (↑1).subtype ↑↑(differentIdeal ℤ 𝒪)) ≃ₗ[𝒪]
    ↥↑(↑(differentIdeal ℤ 𝒪))⁻¹ ⧸ Submodule.comap (↑(↑(differentIdeal ℤ 𝒪))⁻¹).subtype ↑1
this :
  Nat.card (↥↑1 ⧸ Submodule.comap (↑1).subtype ↑↑(differentIdeal ℤ 𝒪)) =
    Nat.card (↥↑(↑(differentIdeal ℤ 𝒪))⁻¹ ⧸ Submodule.comap (↑(↑(differentIdeal ℤ 𝒪))⁻¹).subtype ↑1)
b : Basis (Free.ChooseBasisIndex ℤ (𝓞 K)) ℚ K := integralBasis K
b' : Basis (Free.ChooseBasisIndex ℤ (𝓞 K)) ℚ K := (Algebra.traceForm ℚ K).dualBasis ⋯ b
hb : Submodule.span ℤ (Set.range ⇑b) = Submodule.restrictScalars ℤ 1
⊢ ↑1 ≤ ↑(FractionalIdeal.dual ℤ ℚ 1)

K : Type u_1
𝒪 : Type u_2
inst✝⁷ : Field K
inst✝⁶ : NumberField K
inst✝⁵ : CommRing 𝒪
inst✝⁴ : Algebra 𝒪 K
inst✝³ : IsFractionRing 𝒪 K
inst✝² : IsDedekindDomain 𝒪
inst✝¹ : CharZero 𝒪
inst✝ : Module.Finite ℤ 𝒪
this✝ :
  (↥↑1 ⧸ Submodule.comap (↑1).subtype ↑↑(differentIdeal ℤ 𝒪)) ≃ₗ[𝒪]
    ↥↑(↑(differentIdeal ℤ 𝒪))⁻¹ ⧸ Submodule.comap (↑(↑(differentIdeal ℤ 𝒪))⁻¹).subtype ↑1
this :
  Nat.card (↥↑1 ⧸ Submodule.comap (↑1).subtype ↑↑(differentIdeal ℤ 𝒪)) =
    Nat.card (↥↑(↑(differentIdeal ℤ 𝒪))⁻¹ ⧸ Submodule.comap (↑(↑(differentIdeal ℤ 𝒪))⁻¹).subtype ↑1)
b : Basis (Free.ChooseBasisIndex ℤ (𝓞 K)) ℚ K := ⋯
b' : Basis (Free.ChooseBasisIndex ℤ (𝓞 K)) ℚ K := ⋯
hb : Submodule.span ℤ (Set.range ⇑b) = Submodule.restrictScalars ℤ 1
⊢ Submonoid 𝒪