Module: Mathlib.AlgebraicGeometry.Modules.Tilde

Goal state before:
pp: R : CommRingCat
M : (Spec R).Modules
V : (Spec R).Opens
ι : Type u_1
inst✝ : Finite ι
g : ι → ↑R
hg : V = ⨆ i, basicOpen (g i)
h₁ : ∀ (i : ι), Aux M (basicOpen (g i))
h₂ : ∀ (i j : ι), Aux M (basicOpen (g i * g j))
hgle : ∀ (i : ι), basicOpen (g i) ≤ V
hug : ∀ (i : ι) (m : ℕ), IsUnit ((algebraMap (↑R) (Module.End ↑R ↑Γ(M, basicOpen (g i)))) (g i ^ m))
f : ↑R
hf : basicOpen f ≤ V
s : ↑Γ(M, basicOpen f)
hfgi : ∀ (i : ι), basicOpen (f * g i) ≤ basicOpen (g i)
s' : (i : ι) → ↑Γ(M, basicOpen (f * g i)) := fun i ↦ (ConcreteCategory.hom (M.presheaf.map (homOfLE ⋯).op)) s
N : ℕ
t : (i : ι) → ↑Γ(M, basicOpen (g i))
ht : ∀ (i : ι), f ^ N • s' i = (ConcreteCategory.hom (M.presheaf.map (homOfLE ⋯).op)) (t i)
⊢ ∃ K,
    ∀ (i j : ι),
      (ConcreteCategory.hom (M.presheaf.map (homOfLE ⋯).op)) (f ^ K • t i) =
        (ConcreteCategory.hom (M.presheaf.map (homOfLE ⋯).op)) (f ^ K • t j)

Tactic:
have (i j : ι) : ∃ (m : ℕ),
          M.presheaf.map (homOfLE (basicOpen_mul_le_left (g i) (g j))).op (f ^ m • t i) =
            M.presheaf.map (homOfLE (basicOpen_mul_le_right (g i) (g j))).op (f ^ m • t j) := by
        have := (h₂ i j).uniqueness (f * (g i * g j)) (basicOpen_mul_le_right _ _)
          (M.presheaf.map (homOfLE (basicOpen_mul_le_left (g i) (g j))).op (t i) -
            M.presheaf.map (homOfLE (basicOpen_mul_le_right (g i) (g j))).op (t j)) ?_
        · obtain ⟨m, hm⟩ := this
          use m
          apply (M.isSMulRegular_of_le_basicOpen le_rfl).pow m
          simpa [M.map_smul_Spec _ (f ^ m), ← mul_smul, ← mul_smul, ← mul_pow, ← mul_comm f,
            smul_sub, sub_eq_zero] using hm
        · have hfgigi : basicOpen (f * (g i * g j)) ≤ basicOpen (f * g i) := by
            rw [← mul_assoc]
            exact basicOpen_mul_le_left _ _
          have hfgigj : basicOpen (f * (g i * g j)) ≤ basicOpen (f * g j) := by
            rw [mul_comm (g i) (g j), ← mul_assoc]
            exact basicOpen_mul_le_left _ _
          rw [map_sub, ← M.presheaf.map_comp_apply, ← op_comp, ← M.presheaf.map_comp_apply,
            ← op_comp, homOfLE_comp, homOfLE_comp, ← homOfLE_comp hfgigi (hfgi i),
            ← homOfLE_comp hfgigj (hfgi j), op_comp, M.presheaf.map_comp_apply, ← ht i,
            M.map_smul_Spec, ← M.presheaf.map_comp_apply, ← op_comp, homOfLE_comp, op_comp,
            M.presheaf.map_comp_apply, ← ht j, M.map_smul_Spec, ← M.presheaf.map_comp_apply,
            ← op_comp, homOfLE_comp]
          simp

Goal state after:
R : CommRingCat
M : (Spec R).Modules
V : (Spec R).Opens
ι : Type u_1
inst✝ : Finite ι
g : ι → ↑R
hg : V = ⨆ i, basicOpen (g i)
h₁ : ∀ (i : ι), Aux M (basicOpen (g i))
h₂ : ∀ (i j : ι), Aux M (basicOpen (g i * g j))
hgle : ∀ (i : ι), basicOpen (g i) ≤ V
hug : ∀ (i : ι) (m : ℕ), IsUnit ((algebraMap (↑R) (Module.End ↑R ↑Γ(M, basicOpen (g i)))) (g i ^ m))
f : ↑R
hf : basicOpen f ≤ V
s : ↑Γ(M, basicOpen f)
hfgi : ∀ (i : ι), basicOpen (f * g i) ≤ basicOpen (g i)
s' : (i : ι) → ↑Γ(M, basicOpen (f * g i)) := fun i ↦ (ConcreteCategory.hom (M.presheaf.map (homOfLE ⋯).op)) s
N : ℕ
t : (i : ι) → ↑Γ(M, basicOpen (g i))
ht : ∀ (i : ι), f ^ N • s' i = (ConcreteCategory.hom (M.presheaf.map (homOfLE ⋯).op)) (t i)
this :
  ∀ (i j : ι),
    ∃ m,
      (ConcreteCategory.hom (M.presheaf.map (homOfLE ⋯).op)) (f ^ m • t i) =
        (ConcreteCategory.hom (M.presheaf.map (homOfLE ⋯).op)) (f ^ m • t j)
⊢ ∃ K,
    ∀ (i j : ι),
      (ConcreteCategory.hom (M.presheaf.map (homOfLE ⋯).op)) (f ^ K • t i) =
        (ConcreteCategory.hom (M.presheaf.map (homOfLE ⋯).op)) (f ^ K • t j)