Module: Mathlib.MeasureTheory.Integral.DivergenceTheorem

Goal state before:
pp: case inr
E : Type u
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
f g : ℝ × ℝ → E
f' g' : ℝ × ℝ → ℝ × ℝ →L[ℝ] E
a₁ a₂ b₁ b₂ : ℝ
s : Set (ℝ × ℝ)
hs : s.Countable
Hcf : ContinuousOn f ([[a₁, b₁]] ×ˢ [[a₂, b₂]])
Hcg : ContinuousOn g ([[a₁, b₁]] ×ˢ [[a₂, b₂]])
Hdf : ∀ x ∈ Set.Ioo (min a₁ b₁) (max a₁ b₁) ×ˢ Set.Ioo (min a₂ b₂) (max a₂ b₂) \ s, HasFDerivAt f (f' x) x
Hdg : ∀ x ∈ Set.Ioo (min a₁ b₁) (max a₁ b₁) ×ˢ Set.Ioo (min a₂ b₂) (max a₂ b₂) \ s, HasFDerivAt g (g' x) x
Hi : IntegrableOn (fun x ↦ (f' x) (1, 0) + (g' x) (0, 1)) ([[a₁, b₁]] ×ˢ [[a₂, b₂]]) volume
this :
  ∀ (a₁ b₁ : ℝ),
    ContinuousOn f ([[a₁, b₁]] ×ˢ [[a₂, b₂]]) →
      ContinuousOn g ([[a₁, b₁]] ×ˢ [[a₂, b₂]]) →
        (∀ x ∈ Set.Ioo (min a₁ b₁) (max a₁ b₁) ×ˢ Set.Ioo (min a₂ b₂) (max a₂ b₂) \ s, HasFDerivAt f (f' x) x) →
          (∀ x ∈ Set.Ioo (min a₁ b₁) (max a₁ b₁) ×ˢ Set.Ioo (min a₂ b₂) (max a₂ b₂) \ s, HasFDerivAt g (g' x) x) →
            IntegrableOn (fun x ↦ (f' x) (1, 0) + (g' x) (0, 1)) ([[a₁, b₁]] ×ˢ [[a₂, b₂]]) volume →
              a₁ ≤ b₁ →
                ∫ (x : ℝ) in a₁..b₁, ∫ (y : ℝ) in a₂..b₂, (f' (x, y)) (1, 0) + (g' (x, y)) (0, 1) =
                  (((∫ (x : ℝ) in a₁..b₁, g (x, b₂)) - ∫ (x : ℝ) in a₁..b₁, g (x, a₂)) +
                      ∫ (y : ℝ) in a₂..b₂, f (b₁, y)) -
                    ∫ (y : ℝ) in a₂..b₂, f (a₁, y)
h₁ : ¬a₁ ≤ b₁
⊢ ∫ (x : ℝ) in a₁..b₁, ∫ (y : ℝ) in a₂..b₂, (f' (x, y)) (1, 0) + (g' (x, y)) (0, 1) =
    (((∫ (x : ℝ) in a₁..b₁, g (x, b₂)) - ∫ (x : ℝ) in a₁..b₁, g (x, a₂)) + ∫ (y : ℝ) in a₂..b₂, f (b₁, y)) -
      ∫ (y : ℝ) in a₂..b₂, f (a₁, y)

pp: E : Type u
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
f g : ℝ × ℝ → E
f' g' : ℝ × ℝ → ℝ × ℝ →L[ℝ] E
a₂ b₂ : ℝ
s : Set (ℝ × ℝ)
hs : s.Countable
a₁ b₁ : ℝ
Hcf : ContinuousOn f ([[a₁, b₁]] ×ˢ [[a₂, b₂]])
Hcg : ContinuousOn g ([[a₁, b₁]] ×ˢ [[a₂, b₂]])
Hdf : ∀ x ∈ Set.Ioo (min a₁ b₁) (max a₁ b₁) ×ˢ Set.Ioo (min a₂ b₂) (max a₂ b₂) \ s, HasFDerivAt f (f' x) x
Hdg : ∀ x ∈ Set.Ioo (min a₁ b₁) (max a₁ b₁) ×ˢ Set.Ioo (min a₂ b₂) (max a₂ b₂) \ s, HasFDerivAt g (g' x) x
Hi : IntegrableOn (fun x ↦ (f' x) (1, 0) + (g' x) (0, 1)) ([[a₁, b₁]] ×ˢ [[a₂, b₂]]) volume
h₁ : a₁ ≤ b₁
⊢ ∫ (x : ℝ) in a₁..b₁, ∫ (y : ℝ) in a₂..b₂, (f' (x, y)) (1, 0) + (g' (x, y)) (0, 1) =
    (((∫ (x : ℝ) in a₁..b₁, g (x, b₂)) - ∫ (x : ℝ) in a₁..b₁, g (x, a₂)) + ∫ (y : ℝ) in a₂..b₂, f (b₁, y)) -
      ∫ (y : ℝ) in a₂..b₂, f (a₁, y)

Tactic:
· specialize this b₁ a₁
    rw [uIcc_comm b₁ a₁, min_comm b₁ a₁, max_comm b₁ a₁] at this
    simp only [intervalIntegral.integral_symm b₁ a₁]
    refine (congr_arg Neg.neg (this Hcf Hcg Hdf Hdg Hi (le_of_not_ge h₁))).trans ?_; abel

Goal state after:
E : Type u
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
f g : ℝ × ℝ → E
f' g' : ℝ × ℝ → ℝ × ℝ →L[ℝ] E
a₂ b₂ : ℝ
s : Set (ℝ × ℝ)
hs : s.Countable
a₁ b₁ : ℝ
Hcf : ContinuousOn f ([[a₁, b₁]] ×ˢ [[a₂, b₂]])
Hcg : ContinuousOn g ([[a₁, b₁]] ×ˢ [[a₂, b₂]])
Hdf : ∀ x ∈ Set.Ioo (min a₁ b₁) (max a₁ b₁) ×ˢ Set.Ioo (min a₂ b₂) (max a₂ b₂) \ s, HasFDerivAt f (f' x) x
Hdg : ∀ x ∈ Set.Ioo (min a₁ b₁) (max a₁ b₁) ×ˢ Set.Ioo (min a₂ b₂) (max a₂ b₂) \ s, HasFDerivAt g (g' x) x
Hi : IntegrableOn (fun x ↦ (f' x) (1, 0) + (g' x) (0, 1)) ([[a₁, b₁]] ×ˢ [[a₂, b₂]]) volume
h₁ : a₁ ≤ b₁
⊢ ∫ (x : ℝ) in a₁..b₁, ∫ (y : ℝ) in a₂..b₂, (f' (x, y)) (1, 0) + (g' (x, y)) (0, 1) =
    (((∫ (x : ℝ) in a₁..b₁, g (x, b₂)) - ∫ (x : ℝ) in a₁..b₁, g (x, a₂)) + ∫ (y : ℝ) in a₂..b₂, f (b₁, y)) -
      ∫ (y : ℝ) in a₂..b₂, f (a₁, y)