-- Mathlib/Algebra/Module/ZLattice/Covolume.lean
theorem tendsto_card_le_div {X : Set (ι → ℝ)} (hX : ∀ ⦃x⦄ ⦃r : ℝ⦄, x ∈ X → 0 < r → r • x ∈ X)
    {F : (ι → ℝ) → ℝ} (h₁ : ∀ x ⦃r : ℝ⦄, 0 ≤ r →  F (r • x) = r ^ card ι * (F x))
    (h₂ : IsBounded {x ∈ X | F x ≤ 1}) (h₃ : MeasurableSet {x ∈ X | F x ≤ 1})
    (h₄ : volume (frontier {x | x ∈ X ∧ F x ≤ 1}) = 0) [Nonempty ι] :
    Tendsto (fun c : ℝ ↦
      Nat.card ({x ∈ X | F x ≤ c} ∩ L : Set (ι → ℝ)) / (c : ℝ))
        atTop (𝓝 ((volume {x ∈ X | F x ≤ 1}).toReal / covolume L))

Proof state:
ι : Type u_1
inst✝³ : Fintype ι
L : Submodule ℤ (ι → ℝ)
inst✝² : DiscreteTopology ↥L
inst✝¹ : IsZLattice ℝ L
X : Set (ι → ℝ)
hX : ∀ ⦃x : ι → ℝ⦄ ⦃r : ℝ⦄, x ∈ X → 0 < r → r • x ∈ X
F : (ι → ℝ) → ℝ
h₁ : ∀ (x : ι → ℝ) ⦃r : ℝ⦄, 0 ≤ r → F (r • x) = r ^ card ι * F x
h₂ : Bornology.IsBounded {x | x ∈ X ∧ F x ≤ 1}
h₃ : MeasurableSet {x | x ∈ X ∧ F x ≤ 1}
h₄ : volume (frontier {x | x ∈ X ∧ F x ≤ 1}) = 0
inst✝ : Nonempty ι
e : Free.ChooseBasisIndex ℤ ↥L ≃ ι := equivOfCardEq ⋯
b : Basis ι ℤ ↥L := (Free.chooseBasis ℤ ↥L).reindex e
⊢ volume (frontier (⇑(Basis.ofZLatticeBasis ℝ L b).equivFun '' {x | x ∈ X ∧ F x ≤ 1})) = 0

Tactic:
rw [frontier_equivFun, volume_image_eq_volume_div_covolume, h₄, ENNReal.zero_div]

Result:
no goals

Proof state:
ι : Type u_1
inst✝³ : Fintype ι
L : Submodule ℤ (ι → ℝ)
inst✝² : DiscreteTopology ↥L
inst✝¹ : IsZLattice ℝ L
X : Set (ι → ℝ)
hX : ∀ ⦃x : ι → ℝ⦄ ⦃r : ℝ⦄, x ∈ X → 0 < r → r • x ∈ X
F : (ι → ℝ) → ℝ
h₁ : ∀ (x : ι → ℝ) ⦃r : ℝ⦄, 0 ≤ r → F (r • x) = r ^ card ι * F x
h₂ : Bornology.IsBounded {x | x ∈ X ∧ F x ≤ 1}
h₃ : MeasurableSet {x | x ∈ X ∧ F x ≤ 1}
h₄ : volume (frontier {x | x ∈ X ∧ F x ≤ 1}) = 0
inst✝ : Nonempty ι
⊢ card (Free.ChooseBasisIndex ℤ ↥L) = card ι

Tactic:
rw [← finrank_eq_card_chooseBasisIndex, ZLattice.rank ℝ, finrank_fintype_fun_eq_card]

Result:
no goals

Proof state:
ι : Type u_1
inst✝³ : Fintype ι
L : Submodule ℤ (ι → ℝ)
inst✝² : DiscreteTopology ↥L
inst✝¹ : IsZLattice ℝ L
X : Set (ι → ℝ)
hX : ∀ ⦃x : ι → ℝ⦄ ⦃r : ℝ⦄, x ∈ X → 0 < r → r • x ∈ X
F : (ι → ℝ) → ℝ
h₁ : ∀ (x : ι → ℝ) ⦃r : ℝ⦄, 0 ≤ r → F (r • x) = r ^ card ι * F x
h₂ : Bornology.IsBounded {x | x ∈ X ∧ F x ≤ 1}
h₃ : MeasurableSet {x | x ∈ X ∧ F x ≤ 1}
h₄ : volume (frontier {x | x ∈ X ∧ F x ≤ 1}) = 0
inst✝ : Nonempty ι
e : Free.ChooseBasisIndex ℤ ↥L ≃ ι := equivOfCardEq ⋯
⊢ Tendsto (fun c => ↑(Nat.card ↑({x | x ∈ X ∧ F x ≤ c} ∩ ↑L)) / c) atTop
    (𝓝 ((volume {x | x ∈ X ∧ F x ≤ 1}).toReal / covolume L volume))

Tactic:
let b := (Module.Free.chooseBasis ℤ L).reindex e

Result:
ι : Type u_1
inst✝³ : Fintype ι
L : Submodule ℤ (ι → ℝ)
inst✝² : DiscreteTopology ↥L
inst✝¹ : IsZLattice ℝ L
X : Set (ι → ℝ)
hX : ∀ ⦃x : ι → ℝ⦄ ⦃r : ℝ⦄, x ∈ X → 0 < r → r • x ∈ X
F : (ι → ℝ) → ℝ
h₁ : ∀ (x : ι → ℝ) ⦃r : ℝ⦄, 0 ≤ r → F (r • x) = r ^ card ι * F x
h₂ : Bornology.IsBounded {x | x ∈ X ∧ F x ≤ 1}
h₃ : MeasurableSet {x | x ∈ X ∧ F x ≤ 1}
h₄ : volume (frontier {x | x ∈ X ∧ F x ≤ 1}) = 0
inst✝ : Nonempty ι
e : Free.ChooseBasisIndex ℤ ↥L ≃ ι := equivOfCardEq ⋯
b : Basis ι ℤ ↥L := (Free.chooseBasis ℤ ↥L).reindex e
⊢ Tendsto (fun c => ↑(Nat.card ↑({x | x ∈ X ∧ F x ≤ c} ∩ ↑L)) / c) atTop
    (𝓝 ((volume {x | x ∈ X ∧ F x ≤ 1}).toReal / covolume L volume))

Proof state:
ι : Type u_1
inst✝³ : Fintype ι
L : Submodule ℤ (ι → ℝ)
inst✝² : DiscreteTopology ↥L
inst✝¹ : IsZLattice ℝ L
X : Set (ι → ℝ)
hX : ∀ ⦃x : ι → ℝ⦄ ⦃r : ℝ⦄, x ∈ X → 0 < r → r • x ∈ X
F : (ι → ℝ) → ℝ
h₁ : ∀ (x : ι → ℝ) ⦃r : ℝ⦄, 0 ≤ r → F (r • x) = r ^ card ι * F x
h₂ : Bornology.IsBounded {x | x ∈ X ∧ F x ≤ 1}
h₃ : MeasurableSet {x | x ∈ X ∧ F x ≤ 1}
h₄ : volume (frontier {x | x ∈ X ∧ F x ≤ 1}) = 0
inst✝ : Nonempty ι
⊢ Free.ChooseBasisIndex ℤ ↥L ≃ ι

Tactic:
refine Fintype.equivOfCardEq ?_

Result:
ι : Type u_1
inst✝³ : Fintype ι
L : Submodule ℤ (ι → ℝ)
inst✝² : DiscreteTopology ↥L
inst✝¹ : IsZLattice ℝ L
X : Set (ι → ℝ)
hX : ∀ ⦃x : ι → ℝ⦄ ⦃r : ℝ⦄, x ∈ X → 0 < r → r • x ∈ X
F : (ι → ℝ) → ℝ
h₁ : ∀ (x : ι → ℝ) ⦃r : ℝ⦄, 0 ≤ r → F (r • x) = r ^ card ι * F x
h₂ : Bornology.IsBounded {x | x ∈ X ∧ F x ≤ 1}
h₃ : MeasurableSet {x | x ∈ X ∧ F x ≤ 1}
h₄ : volume (frontier {x | x ∈ X ∧ F x ≤ 1}) = 0
inst✝ : Nonempty ι
⊢ card (Free.ChooseBasisIndex ℤ ↥L) = card ι

Proof state:
ι : Type u_1
inst✝³ : Fintype ι
L : Submodule ℤ (ι → ℝ)
inst✝² : DiscreteTopology ↥L
inst✝¹ : IsZLattice ℝ L
X : Set (ι → ℝ)
hX : ∀ ⦃x : ι → ℝ⦄ ⦃r : ℝ⦄, x ∈ X → 0 < r → r • x ∈ X
F : (ι → ℝ) → ℝ
h₁ : ∀ (x : ι → ℝ) ⦃r : ℝ⦄, 0 ≤ r → F (r • x) = r ^ card ι * F x
h₂ : Bornology.IsBounded {x | x ∈ X ∧ F x ≤ 1}
h₃ : MeasurableSet {x | x ∈ X ∧ F x ≤ 1}
h₄ : volume (frontier {x | x ∈ X ∧ F x ≤ 1}) = 0
inst✝ : Nonempty ι
e : Free.ChooseBasisIndex ℤ ↥L ≃ ι := equivOfCardEq ⋯
b : Basis ι ℤ ↥L := (Free.chooseBasis ℤ ↥L).reindex e
⊢ Tendsto (fun c => ↑(Nat.card ↑({x | x ∈ X ∧ F x ≤ c} ∩ ↑L)) / c) atTop
    (𝓝 ((volume {x | x ∈ X ∧ F x ≤ 1}).toReal / covolume L volume))

Tactic:
convert tendsto_card_le_div'' b hX h₁ h₂ h₃ ?_

Result:
case h.e'_5.h.e'_3
ι : Type u_1
inst✝³ : Fintype ι
L : Submodule ℤ (ι → ℝ)
inst✝² : DiscreteTopology ↥L
inst✝¹ : IsZLattice ℝ L
X : Set (ι → ℝ)
hX : ∀ ⦃x : ι → ℝ⦄ ⦃r : ℝ⦄, x ∈ X → 0 < r → r • x ∈ X
F : (ι → ℝ) → ℝ
h₁ : ∀ (x : ι → ℝ) ⦃r : ℝ⦄, 0 ≤ r → F (r • x) = r ^ card ι * F x
h₂ : Bornology.IsBounded {x | x ∈ X ∧ F x ≤ 1}
h₃ : MeasurableSet {x | x ∈ X ∧ F x ≤ 1}
h₄ : volume (frontier {x | x ∈ X ∧ F x ≤ 1}) = 0
inst✝ : Nonempty ι
e : Free.ChooseBasisIndex ℤ ↥L ≃ ι := equivOfCardEq ⋯
b : Basis ι ℤ ↥L := (Free.chooseBasis ℤ ↥L).reindex e
⊢ (volume {x | x ∈ X ∧ F x ≤ 1}).toReal / covolume L volume =
    (volume (⇑(Basis.ofZLatticeBasis ℝ L b).equivFun '' {x | x ∈ X ∧ F x ≤ 1})).toReal

ι : Type u_1
inst✝³ : Fintype ι
L : Submodule ℤ (ι → ℝ)
inst✝² : DiscreteTopology ↥L
inst✝¹ : IsZLattice ℝ L
X : Set (ι → ℝ)
hX : ∀ ⦃x : ι → ℝ⦄ ⦃r : ℝ⦄, x ∈ X → 0 < r → r • x ∈ X
F : (ι → ℝ) → ℝ
h₁ : ∀ (x : ι → ℝ) ⦃r : ℝ⦄, 0 ≤ r → F (r • x) = r ^ card ι * F x
h₂ : Bornology.IsBounded {x | x ∈ X ∧ F x ≤ 1}
h₃ : MeasurableSet {x | x ∈ X ∧ F x ≤ 1}
h₄ : volume (frontier {x | x ∈ X ∧ F x ≤ 1}) = 0
inst✝ : Nonempty ι
e : Free.ChooseBasisIndex ℤ ↥L ≃ ι := equivOfCardEq ⋯
b : Basis ι ℤ ↥L := (Free.chooseBasis ℤ ↥L).reindex e
⊢ volume (frontier (⇑(Basis.ofZLatticeBasis ℝ L b).equivFun '' {x | x ∈ X ∧ F x ≤ 1})) = 0

Proof state:
ι : Type u_1
inst✝³ : Fintype ι
L : Submodule ℤ (ι → ℝ)
inst✝² : DiscreteTopology ↥L
inst✝¹ : IsZLattice ℝ L
X : Set (ι → ℝ)
hX : ∀ ⦃x : ι → ℝ⦄ ⦃r : ℝ⦄, x ∈ X → 0 < r → r • x ∈ X
F : (ι → ℝ) → ℝ
h₁ : ∀ (x : ι → ℝ) ⦃r : ℝ⦄, 0 ≤ r → F (r • x) = r ^ card ι * F x
h₂ : Bornology.IsBounded {x | x ∈ X ∧ F x ≤ 1}
h₃ : MeasurableSet {x | x ∈ X ∧ F x ≤ 1}
h₄ : volume (frontier {x | x ∈ X ∧ F x ≤ 1}) = 0
inst✝ : Nonempty ι
⊢ Tendsto (fun c => ↑(Nat.card ↑({x | x ∈ X ∧ F x ≤ c} ∩ ↑L)) / c) atTop
    (𝓝 ((volume {x | x ∈ X ∧ F x ≤ 1}).toReal / covolume L volume))

Tactic:
let e : Free.ChooseBasisIndex ℤ ↥L ≃ ι := by
  refine Fintype.equivOfCardEq ?_
  rw [← finrank_eq_card_chooseBasisIndex, ZLattice.rank ℝ, finrank_fintype_fun_eq_card]

Result:
ι : Type u_1
inst✝³ : Fintype ι
L : Submodule ℤ (ι → ℝ)
inst✝² : DiscreteTopology ↥L
inst✝¹ : IsZLattice ℝ L
X : Set (ι → ℝ)
hX : ∀ ⦃x : ι → ℝ⦄ ⦃r : ℝ⦄, x ∈ X → 0 < r → r • x ∈ X
F : (ι → ℝ) → ℝ
h₁ : ∀ (x : ι → ℝ) ⦃r : ℝ⦄, 0 ≤ r → F (r • x) = r ^ card ι * F x
h₂ : Bornology.IsBounded {x | x ∈ X ∧ F x ≤ 1}
h₃ : MeasurableSet {x | x ∈ X ∧ F x ≤ 1}
h₄ : volume (frontier {x | x ∈ X ∧ F x ≤ 1}) = 0
inst✝ : Nonempty ι
e : Free.ChooseBasisIndex ℤ ↥L ≃ ι := equivOfCardEq ⋯
⊢ Tendsto (fun c => ↑(Nat.card ↑({x | x ∈ X ∧ F x ≤ c} ∩ ↑L)) / c) atTop
    (𝓝 ((volume {x | x ∈ X ∧ F x ≤ 1}).toReal / covolume L volume))