Theorem: MeasureTheory.integral_divergence_prod_Icc_of_hasFDerivWithinAt_off_countable_of_le
File: Mathlib/MeasureTheory/Integral/DivergenceTheorem.lean

Proof steps:
state_before: E : Type u
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
f g : ℝ × ℝ → E
f' g' : ℝ × ℝ → ℝ × ℝ →L[ℝ] E
a b : ℝ × ℝ
hle : a ≤ b
s : Set (ℝ × ℝ)
hs : s.Countable
Hcf : ContinuousOn f (Set.Icc a b)
Hcg : ContinuousOn g (Set.Icc a b)
Hdf : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt f (f' x) x
Hdg : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt g (g' x) x
Hi : IntegrableOn (fun x => (f' x) (1, 0) + (g' x) (0, 1)) (Set.Icc a b) volume
e : (ℝ × ℝ) ≃L[ℝ] Fin 2 → ℝ := (ContinuousLinearEquiv.finTwoArrow ℝ ℝ).symm
⊢ ∫ (x : ℝ × ℝ) in Set.Icc a b, (f' x) (1, 0) + (g' x) (0, 1) =
    ∑ i : Fin 2,
      ((∫ (x : Fin 1 → ℝ) in Set.Icc (e a ∘ i.succAbove) (e b ∘ i.succAbove),
          ![f, g] i (e.symm (i.insertNth (e b i) x))) -
        ∫ (x : Fin 1 → ℝ) in Set.Icc (e a ∘ i.succAbove) (e b ∘ i.succAbove),
          ![f, g] i (e.symm (i.insertNth (e a i) x)))
state_after: case refine_1
E : Type u
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
f g : ℝ × ℝ → E
f' g' : ℝ × ℝ → ℝ × ℝ →L[ℝ] E
a b : ℝ × ℝ
hle : a ≤ b
s : Set (ℝ × ℝ)
hs : s.Countable
Hcf : ContinuousOn f (Set.Icc a b)
Hcg : ContinuousOn g (Set.Icc a b)
Hdf : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt f (f' x) x
Hdg : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt g (g' x) x
Hi : IntegrableOn (fun x => (f' x) (1, 0) + (g' x) (0, 1)) (Set.Icc a b) volume
e : (ℝ × ℝ) ≃L[ℝ] Fin 2 → ℝ := (ContinuousLinearEquiv.finTwoArrow ℝ ℝ).symm
⊢ ∀ (x y : ℝ × ℝ), e x ≤ e y ↔ x ≤ y

case refine_2
E : Type u
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
f g : ℝ × ℝ → E
f' g' : ℝ × ℝ → ℝ × ℝ →L[ℝ] E
a b : ℝ × ℝ
hle : a ≤ b
s : Set (ℝ × ℝ)
hs : s.Countable
Hcf : ContinuousOn f (Set.Icc a b)
Hcg : ContinuousOn g (Set.Icc a b)
Hdf : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt f (f' x) x
Hdg : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt g (g' x) x
Hi : IntegrableOn (fun x => (f' x) (1, 0) + (g' x) (0, 1)) (Set.Icc a b) volume
e : (ℝ × ℝ) ≃L[ℝ] Fin 2 → ℝ := (ContinuousLinearEquiv.finTwoArrow ℝ ℝ).symm
⊢ MeasurePreserving (⇑e) volume volume

case refine_3
E : Type u
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
f g : ℝ × ℝ → E
f' g' : ℝ × ℝ → ℝ × ℝ →L[ℝ] E
a b : ℝ × ℝ
hle : a ≤ b
s : Set (ℝ × ℝ)
hs : s.Countable
Hcf : ContinuousOn f (Set.Icc a b)
Hcg : ContinuousOn g (Set.Icc a b)
Hdf : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt f (f' x) x
Hdg : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt g (g' x) x
Hi : IntegrableOn (fun x => (f' x) (1, 0) + (g' x) (0, 1)) (Set.Icc a b) volume
e : (ℝ × ℝ) ≃L[ℝ] Fin 2 → ℝ := (ContinuousLinearEquiv.finTwoArrow ℝ ℝ).symm
⊢ ∀ (i : Fin (1 + 1)), ContinuousOn (![f, g] i) (Set.Icc a b)

case refine_4
E : Type u
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
f g : ℝ × ℝ → E
f' g' : ℝ × ℝ → ℝ × ℝ →L[ℝ] E
a b : ℝ × ℝ
hle : a ≤ b
s : Set (ℝ × ℝ)
hs : s.Countable
Hcf : ContinuousOn f (Set.Icc a b)
Hcg : ContinuousOn g (Set.Icc a b)
Hdf : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt f (f' x) x
Hdg : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt g (g' x) x
Hi : IntegrableOn (fun x => (f' x) (1, 0) + (g' x) (0, 1)) (Set.Icc a b) volume
e : (ℝ × ℝ) ≃L[ℝ] Fin 2 → ℝ := (ContinuousLinearEquiv.finTwoArrow ℝ ℝ).symm
x : ℝ × ℝ
hx : x ∈ interior (Set.Icc a b) \ s
⊢ ∀ (i : Fin (1 + 1)), HasFDerivAt (![f, g] i) (![f', g'] i x) x

case refine_5
E : Type u
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
f g : ℝ × ℝ → E
f' g' : ℝ × ℝ → ℝ × ℝ →L[ℝ] E
a b : ℝ × ℝ
hle : a ≤ b
s : Set (ℝ × ℝ)
hs : s.Countable
Hcf : ContinuousOn f (Set.Icc a b)
Hcg : ContinuousOn g (Set.Icc a b)
Hdf : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt f (f' x) x
Hdg : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt g (g' x) x
Hi : IntegrableOn (fun x => (f' x) (1, 0) + (g' x) (0, 1)) (Set.Icc a b) volume
e : (ℝ × ℝ) ≃L[ℝ] Fin 2 → ℝ := (ContinuousLinearEquiv.finTwoArrow ℝ ℝ).symm
⊢ ∀ (x : ℝ × ℝ), (f' x) (1, 0) + (g' x) (0, 1) = ∑ i : Fin (1 + 1), (![f', g'] i x) (e.symm (Pi.single i 1))
tactic: refine integral_divergence_of_hasFDerivWithinAt_off_countable_of_equiv e ?_ ?_ ![f, g]
        ![f', g'] s hs a b hle ?_ (fun x hx => ?_) _ ?_ Hi
state_before: E : Type u
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
f g : ℝ × ℝ → E
f' g' : ℝ × ℝ → ℝ × ℝ →L[ℝ] E
a b : ℝ × ℝ
hle : a ≤ b
s : Set (ℝ × ℝ)
hs : s.Countable
Hcf : ContinuousOn f (Set.Icc a b)
Hcg : ContinuousOn g (Set.Icc a b)
Hdf : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt f (f' x) x
Hdg : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt g (g' x) x
Hi : IntegrableOn (fun x => (f' x) (1, 0) + (g' x) (0, 1)) (Set.Icc a b) volume
e : (ℝ × ℝ) ≃L[ℝ] Fin 2 → ℝ := (ContinuousLinearEquiv.finTwoArrow ℝ ℝ).symm
⊢ ∑ i : Fin 2,
      ((∫ (x : Fin 1 → ℝ) in Set.Icc (e a ∘ i.succAbove) (e b ∘ i.succAbove),
          ![f, g] i (e.symm (i.insertNth (e b i) x))) -
        ∫ (x : Fin 1 → ℝ) in Set.Icc (e a ∘ i.succAbove) (e b ∘ i.succAbove),
          ![f, g] i (e.symm (i.insertNth (e a i) x))) =
    ((∫ (y : ℝ) in Set.Icc a.2 b.2, f (b.1, y)) - ∫ (y : ℝ) in Set.Icc a.2 b.2, f (a.1, y)) +
      ((∫ (x : ℝ) in Set.Icc a.1 b.1, g (x, b.2)) - ∫ (x : ℝ) in Set.Icc a.1 b.1, g (x, a.2))
state_after: E : Type u
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
f g : ℝ × ℝ → E
f' g' : ℝ × ℝ → ℝ × ℝ →L[ℝ] E
a b : ℝ × ℝ
hle : a ≤ b
s : Set (ℝ × ℝ)
hs : s.Countable
Hcf : ContinuousOn f (Set.Icc a b)
Hcg : ContinuousOn g (Set.Icc a b)
Hdf : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt f (f' x) x
Hdg : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt g (g' x) x
Hi : IntegrableOn (fun x => (f' x) (1, 0) + (g' x) (0, 1)) (Set.Icc a b) volume
e : (ℝ × ℝ) ≃L[ℝ] Fin 2 → ℝ := (ContinuousLinearEquiv.finTwoArrow ℝ ℝ).symm
this :
  ∀ (a b : Fin 1 → ℝ) (f : (Fin 1 → ℝ) → E),
    ∫ (x : Fin 1 → ℝ) in Set.Icc a b, f x = ∫ (x : ℝ) in Set.Icc (a 0) (b 0), f fun x_1 => x
⊢ ∑ i : Fin 2,
      ((∫ (x : Fin 1 → ℝ) in Set.Icc (e a ∘ i.succAbove) (e b ∘ i.succAbove),
          ![f, g] i (e.symm (i.insertNth (e b i) x))) -
        ∫ (x : Fin 1 → ℝ) in Set.Icc (e a ∘ i.succAbove) (e b ∘ i.succAbove),
          ![f, g] i (e.symm (i.insertNth (e a i) x))) =
    ((∫ (y : ℝ) in Set.Icc a.2 b.2, f (b.1, y)) - ∫ (y : ℝ) in Set.Icc a.2 b.2, f (a.1, y)) +
      ((∫ (x : ℝ) in Set.Icc a.1 b.1, g (x, b.2)) - ∫ (x : ℝ) in Set.Icc a.1 b.1, g (x, a.2))
tactic: have : ∀ (a b : ℝ¹) (f : ℝ¹ → E),
          ∫ x in Icc a b, f x = ∫ x in Icc (a 0) (b 0), f fun _ => x := fun a b f ↦ by
        convert (((volume_preserving_funUnique (Fin 1) ℝ).symm _).setIntegral_preimage_emb
          (MeasurableEquiv.measurableEmbedding _) f _).symm
        exact ((OrderIso.funUnique (Fin 1) ℝ).symm.preimage_Icc a b).symm
state_before: E : Type u
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
f g : ℝ × ℝ → E
f' g' : ℝ × ℝ → ℝ × ℝ →L[ℝ] E
a b : ℝ × ℝ
hle : a ≤ b
s : Set (ℝ × ℝ)
hs : s.Countable
Hcf : ContinuousOn f (Set.Icc a b)
Hcg : ContinuousOn g (Set.Icc a b)
Hdf : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt f (f' x) x
Hdg : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt g (g' x) x
Hi : IntegrableOn (fun x => (f' x) (1, 0) + (g' x) (0, 1)) (Set.Icc a b) volume
e : (ℝ × ℝ) ≃L[ℝ] Fin 2 → ℝ := (ContinuousLinearEquiv.finTwoArrow ℝ ℝ).symm
this :
  ∀ (a b : Fin 1 → ℝ) (f : (Fin 1 → ℝ) → E),
    ∫ (x : Fin 1 → ℝ) in Set.Icc a b, f x = ∫ (x : ℝ) in Set.Icc (a 0) (b 0), f fun x_1 => x
⊢ ∑ i : Fin 2,
      ((∫ (x : Fin 1 → ℝ) in Set.Icc (e a ∘ i.succAbove) (e b ∘ i.succAbove),
          ![f, g] i (e.symm (i.insertNth (e b i) x))) -
        ∫ (x : Fin 1 → ℝ) in Set.Icc (e a ∘ i.succAbove) (e b ∘ i.succAbove),
          ![f, g] i (e.symm (i.insertNth (e a i) x))) =
    ((∫ (y : ℝ) in Set.Icc a.2 b.2, f (b.1, y)) - ∫ (y : ℝ) in Set.Icc a.2 b.2, f (a.1, y)) +
      ((∫ (x : ℝ) in Set.Icc a.1 b.1, g (x, b.2)) - ∫ (x : ℝ) in Set.Icc a.1 b.1, g (x, a.2))
state_after: E : Type u
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
f g : ℝ × ℝ → E
f' g' : ℝ × ℝ → ℝ × ℝ →L[ℝ] E
a b : ℝ × ℝ
hle : a ≤ b
s : Set (ℝ × ℝ)
hs : s.Countable
Hcf : ContinuousOn f (Set.Icc a b)
Hcg : ContinuousOn g (Set.Icc a b)
Hdf : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt f (f' x) x
Hdg : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt g (g' x) x
Hi : IntegrableOn (fun x => (f' x) (1, 0) + (g' x) (0, 1)) (Set.Icc a b) volume
e : (ℝ × ℝ) ≃L[ℝ] Fin 2 → ℝ := (ContinuousLinearEquiv.finTwoArrow ℝ ℝ).symm
this :
  ∀ (a b : Fin 1 → ℝ) (f : (Fin 1 → ℝ) → E),
    ∫ (x : Fin 1 → ℝ) in Set.Icc a b, f x = ∫ (x : ℝ) in Set.Icc (a 0) (b 0), f fun x_1 => x
⊢ ((∫ (x : ℝ) in Set.Icc ((e a ∘ Fin.succAbove 0) 0) ((e b ∘ Fin.succAbove 0) 0),
          ![f, g] 0 (e.symm (Fin.insertNth 0 (e b 0) fun x_1 => x))) -
        ∫ (x : ℝ) in Set.Icc ((e a ∘ Fin.succAbove 0) 0) ((e b ∘ Fin.succAbove 0) 0),
          ![f, g] 0 (e.symm (Fin.insertNth 0 (e a 0) fun x_1 => x))) +
      ((∫ (x : ℝ) in Set.Icc ((e a ∘ Fin.succAbove 1) 0) ((e b ∘ Fin.succAbove 1) 0),
          ![f, g] 1 (e.symm (Fin.insertNth 1 (e b 1) fun x_1 => x))) -
        ∫ (x : ℝ) in Set.Icc ((e a ∘ Fin.succAbove 1) 0) ((e b ∘ Fin.succAbove 1) 0),
          ![f, g] 1 (e.symm (Fin.insertNth 1 (e a 1) fun x_1 => x))) =
    ((∫ (y : ℝ) in Set.Icc a.2 b.2, f (b.1, y)) - ∫ (y : ℝ) in Set.Icc a.2 b.2, f (a.1, y)) +
      ((∫ (x : ℝ) in Set.Icc a.1 b.1, g (x, b.2)) - ∫ (x : ℝ) in Set.Icc a.1 b.1, g (x, a.2))
tactic: simp only [Fin.sum_univ_two, this]
state_before: E : Type u
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
f g : ℝ × ℝ → E
f' g' : ℝ × ℝ → ℝ × ℝ →L[ℝ] E
a b : ℝ × ℝ
hle : a ≤ b
s : Set (ℝ × ℝ)
hs : s.Countable
Hcf : ContinuousOn f (Set.Icc a b)
Hcg : ContinuousOn g (Set.Icc a b)
Hdf : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt f (f' x) x
Hdg : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt g (g' x) x
Hi : IntegrableOn (fun x => (f' x) (1, 0) + (g' x) (0, 1)) (Set.Icc a b) volume
e : (ℝ × ℝ) ≃L[ℝ] Fin 2 → ℝ := (ContinuousLinearEquiv.finTwoArrow ℝ ℝ).symm
this :
  ∀ (a b : Fin 1 → ℝ) (f : (Fin 1 → ℝ) → E),
    ∫ (x : Fin 1 → ℝ) in Set.Icc a b, f x = ∫ (x : ℝ) in Set.Icc (a 0) (b 0), f fun x_1 => x
⊢ ((∫ (x : ℝ) in Set.Icc ((e a ∘ Fin.succAbove 0) 0) ((e b ∘ Fin.succAbove 0) 0),
          ![f, g] 0 (e.symm (Fin.insertNth 0 (e b 0) fun x_1 => x))) -
        ∫ (x : ℝ) in Set.Icc ((e a ∘ Fin.succAbove 0) 0) ((e b ∘ Fin.succAbove 0) 0),
          ![f, g] 0 (e.symm (Fin.insertNth 0 (e a 0) fun x_1 => x))) +
      ((∫ (x : ℝ) in Set.Icc ((e a ∘ Fin.succAbove 1) 0) ((e b ∘ Fin.succAbove 1) 0),
          ![f, g] 1 (e.symm (Fin.insertNth 1 (e b 1) fun x_1 => x))) -
        ∫ (x : ℝ) in Set.Icc ((e a ∘ Fin.succAbove 1) 0) ((e b ∘ Fin.succAbove 1) 0),
          ![f, g] 1 (e.symm (Fin.insertNth 1 (e a 1) fun x_1 => x))) =
    ((∫ (y : ℝ) in Set.Icc a.2 b.2, f (b.1, y)) - ∫ (y : ℝ) in Set.Icc a.2 b.2, f (a.1, y)) +
      ((∫ (x : ℝ) in Set.Icc a.1 b.1, g (x, b.2)) - ∫ (x : ℝ) in Set.Icc a.1 b.1, g (x, a.2))
state_after: no goals
tactic: rfl
state_before: E : Type u
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
f g : ℝ × ℝ → E
f' g' : ℝ × ℝ → ℝ × ℝ →L[ℝ] E
a b : ℝ × ℝ
hle : a ≤ b
s : Set (ℝ × ℝ)
hs : s.Countable
Hcf : ContinuousOn f (Set.Icc a b)
Hcg : ContinuousOn g (Set.Icc a b)
Hdf : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt f (f' x) x
Hdg : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt g (g' x) x
Hi : IntegrableOn (fun x => (f' x) (1, 0) + (g' x) (0, 1)) (Set.Icc a b) volume
e : (ℝ × ℝ) ≃L[ℝ] Fin 2 → ℝ := (ContinuousLinearEquiv.finTwoArrow ℝ ℝ).symm
⊢ ((∫ (y : ℝ) in Set.Icc a.2 b.2, f (b.1, y)) - ∫ (y : ℝ) in Set.Icc a.2 b.2, f (a.1, y)) +
      ((∫ (x : ℝ) in Set.Icc a.1 b.1, g (x, b.2)) - ∫ (x : ℝ) in Set.Icc a.1 b.1, g (x, a.2)) =
    (((∫ (x : ℝ) in a.1 ..b.1, g (x, b.2)) - ∫ (x : ℝ) in a.1 ..b.1, g (x, a.2)) + ∫ (y : ℝ) in a.2 ..b.2, f (b.1, y)) -
      ∫ (y : ℝ) in a.2 ..b.2, f (a.1, y)
state_after: E : Type u
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
f g : ℝ × ℝ → E
f' g' : ℝ × ℝ → ℝ × ℝ →L[ℝ] E
a b : ℝ × ℝ
hle : a ≤ b
s : Set (ℝ × ℝ)
hs : s.Countable
Hcf : ContinuousOn f (Set.Icc a b)
Hcg : ContinuousOn g (Set.Icc a b)
Hdf : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt f (f' x) x
Hdg : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt g (g' x) x
Hi : IntegrableOn (fun x => (f' x) (1, 0) + (g' x) (0, 1)) (Set.Icc a b) volume
e : (ℝ × ℝ) ≃L[ℝ] Fin 2 → ℝ := (ContinuousLinearEquiv.finTwoArrow ℝ ℝ).symm
⊢ ((∫ (y : ℝ) in Set.Icc a.2 b.2, f (b.1, y)) - ∫ (y : ℝ) in Set.Icc a.2 b.2, f (a.1, y)) +
      ((∫ (x : ℝ) in Set.Icc a.1 b.1, g (x, b.2)) - ∫ (x : ℝ) in Set.Icc a.1 b.1, g (x, a.2)) =
    (((∫ (x : ℝ) in Set.Icc a.1 b.1, g (x, b.2)) - ∫ (x : ℝ) in Set.Icc a.1 b.1, g (x, a.2)) +
        ∫ (y : ℝ) in Set.Icc a.2 b.2, f (b.1, y)) -
      ∫ (y : ℝ) in Set.Icc a.2 b.2, f (a.1, y)
tactic: simp only [intervalIntegral.integral_of_le hle.1, intervalIntegral.integral_of_le hle.2,
        setIntegral_congr_set_ae (Ioc_ae_eq_Icc (α := ℝ) (μ := volume))]
state_before: E : Type u
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
f g : ℝ × ℝ → E
f' g' : ℝ × ℝ → ℝ × ℝ →L[ℝ] E
a b : ℝ × ℝ
hle : a ≤ b
s : Set (ℝ × ℝ)
hs : s.Countable
Hcf : ContinuousOn f (Set.Icc a b)
Hcg : ContinuousOn g (Set.Icc a b)
Hdf : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt f (f' x) x
Hdg : ∀ x ∈ Set.Ioo a.1 b.1 ×ˢ Set.Ioo a.2 b.2 \ s, HasFDerivAt g (g' x) x
Hi : IntegrableOn (fun x => (f' x) (1, 0) + (g' x) (0, 1)) (Set.Icc a b) volume
e : (ℝ × ℝ) ≃L[ℝ] Fin 2 → ℝ := (ContinuousLinearEquiv.finTwoArrow ℝ ℝ).symm
⊢ ((∫ (y : ℝ) in Set.Icc a.2 b.2, f (b.1, y)) - ∫ (y : ℝ) in Set.Icc a.2 b.2, f (a.1, y)) +
      ((∫ (x : ℝ) in Set.Icc a.1 b.1, g (x, b.2)) - ∫ (x : ℝ) in Set.Icc a.1 b.1, g (x, a.2)) =
    (((∫ (x : ℝ) in Set.Icc a.1 b.1, g (x, b.2)) - ∫ (x : ℝ) in Set.Icc a.1 b.1, g (x, a.2)) +
        ∫ (y : ℝ) in Set.Icc a.2 b.2, f (b.1, y)) -
      ∫ (y : ℝ) in Set.Icc a.2 b.2, f (a.1, y)
state_after: no goals
tactic: abel