Module: Mathlib.RingTheory.Coprime.Ideal

Goal state before:
pp: case a3
ι : Type u_1
R : Type u_2
inst✝ : CommSemiring R
I : ι → Ideal R
this✝ : DecidableEq ι
a : ι
t : Finset ι
hat : a ∉ t
h : t.Nonempty
ih : (∃ μ, ∑ i ∈ t, ↑(μ i) = 1) ↔ (↑t).Pairwise fun i j ↦ I i ⊔ I j = ⊤
this : Std.Symm fun x1 x2 ↦ I x1 ⊔ I x2 = ⊤
μ : (i : ι) → ↥(⨅ j ∈ Finset.cons a t hat, ⨅ (_ : j ≠ i), I j)
hμ : ↑(μ a) + ∑ x ∈ t, ↑(μ x) = 1
⊢ ∑ i ∈ t, ↑((Pi.single (Exists.choose h) ⟨↑(μ a), ?a1⟩ + fun i ↦ ?m.176) i) = 1

pp: case a4
ι : Type u_1
R : Type u_2
inst✝ : CommSemiring R
I : ι → Ideal R
this✝ : DecidableEq ι
a : ι
t : Finset ι
hat : a ∉ t
h : t.Nonempty
ih : (∃ μ, ∑ i ∈ t, ↑(μ i) = 1) ↔ (↑t).Pairwise fun i j ↦ I i ⊔ I j = ⊤
this : Std.Symm fun x1 x2 ↦ I x1 ⊔ I x2 = ⊤
μ : (i : ι) → ↥(⨅ j ∈ Finset.cons a t hat, ⨅ (_ : j ≠ i), I j)
hμ : ↑(μ a) + ∑ x ∈ t, ↑(μ x) = 1
b : ι
hb : b ∈ ↑t
ab : a ≠ b
⊢ I a ⊔ I b = ⊤

pp: case a1
ι : Type u_1
R : Type u_2
inst✝ : CommSemiring R
I : ι → Ideal R
this✝ : DecidableEq ι
a : ι
t : Finset ι
hat : a ∉ t
h : t.Nonempty
ih : (∃ μ, ∑ i ∈ t, ↑(μ i) = 1) ↔ (↑t).Pairwise fun i j ↦ I i ⊔ I j = ⊤
this : Std.Symm fun x1 x2 ↦ I x1 ⊔ I x2 = ⊤
μ : (i : ι) → ↥(⨅ j ∈ Finset.cons a t hat, ⨅ (_ : j ≠ i), I j)
hμ : ↑(μ a) + ∑ x ∈ t, ↑(μ x) = 1
⊢ ↑(μ a) ∈ ⨅ j ∈ t, ⨅ (_ : j ≠ Exists.choose h), I j

pp: case a2
ι : Type u_1
R : Type u_2
inst✝ : CommSemiring R
I : ι → Ideal R
this✝ : DecidableEq ι
a : ι
t : Finset ι
hat : a ∉ t
h : t.Nonempty
ih : (∃ μ, ∑ i ∈ t, ↑(μ i) = 1) ↔ (↑t).Pairwise fun i j ↦ I i ⊔ I j = ⊤
this : Std.Symm fun x1 x2 ↦ I x1 ⊔ I x2 = ⊤
μ : (i : ι) → ↥(⨅ j ∈ Finset.cons a t hat, ⨅ (_ : j ≠ i), I j)
hμ : ↑(μ a) + ∑ x ∈ t, ↑(μ x) = 1
i : ι
⊢ ↑(μ i) ∈ ⨅ j ∈ t, ⨅ (_ : j ≠ i), I j

Tactic:
case a1 =>
      have := Submodule.coe_mem (μ a)
      rw [mem_iInf] at this ⊢
      --for some reason `simp only [mem_iInf]` times out
      intro i
      specialize this i
      rw [mem_iInf, mem_iInf] at this ⊢
      intro hi _
      apply this (Finset.subset_cons _ hi)
      rintro rfl
      exact hat hi

Goal state after:
case a3
ι : Type u_1
R : Type u_2
inst✝ : CommSemiring R
I : ι → Ideal R
this✝ : DecidableEq ι
a : ι
t : Finset ι
hat : a ∉ t
h : t.Nonempty
ih : (∃ μ, ∑ i ∈ t, ↑(μ i) = 1) ↔ (↑t).Pairwise fun i j ↦ I i ⊔ I j = ⊤
this : Std.Symm fun x1 x2 ↦ I x1 ⊔ I x2 = ⊤
μ : (i : ι) → ↥(⨅ j ∈ Finset.cons a t hat, ⨅ (_ : j ≠ i), I j)
hμ : ↑(μ a) + ∑ x ∈ t, ↑(μ x) = 1
⊢ ∑ i ∈ t, ↑((Pi.single (Exists.choose h) ⟨↑(μ a), ⋯⟩ + fun i ↦ ?m.176) i) = 1

case a4
ι : Type u_1
R : Type u_2
inst✝ : CommSemiring R
I : ι → Ideal R
this✝ : DecidableEq ι
a : ι
t : Finset ι
hat : a ∉ t
h : t.Nonempty
ih : (∃ μ, ∑ i ∈ t, ↑(μ i) = 1) ↔ (↑t).Pairwise fun i j ↦ I i ⊔ I j = ⊤
this : Std.Symm fun x1 x2 ↦ I x1 ⊔ I x2 = ⊤
μ : (i : ι) → ↥(⨅ j ∈ Finset.cons a t hat, ⨅ (_ : j ≠ i), I j)
hμ : ↑(μ a) + ∑ x ∈ t, ↑(μ x) = 1
b : ι
hb : b ∈ ↑t
ab : a ≠ b
⊢ I a ⊔ I b = ⊤

case a2
ι : Type u_1
R : Type u_2
inst✝ : CommSemiring R
I : ι → Ideal R
this✝ : DecidableEq ι
a : ι
t : Finset ι
hat : a ∉ t
h : t.Nonempty
ih : (∃ μ, ∑ i ∈ t, ↑(μ i) = 1) ↔ (↑t).Pairwise fun i j ↦ I i ⊔ I j = ⊤
this : Std.Symm fun x1 x2 ↦ I x1 ⊔ I x2 = ⊤
μ : (i : ι) → ↥(⨅ j ∈ Finset.cons a t hat, ⨅ (_ : j ≠ i), I j)
hμ : ↑(μ a) + ∑ x ∈ t, ↑(μ x) = 1
i : ι
⊢ ↑(μ i) ∈ ⨅ j ∈ t, ⨅ (_ : j ≠ i), I j