Module: Mathlib.AlgebraicTopology.SimplicialSet.AnodyneExtensions.UnionProd

Goal state before:
pp: m✝ : ℕ
k✝ : Fin (m✝ + 1)
n✝ : ℕ
x : (Λ[m✝ + 1, k✝.castSucc].unionProd ∂Δ[n✝]).N
d✝ m : ℕ
k : Fin (m + 1)
n d : ℕ
is it : Fin (d + 1)
s : (Δ[m + 1] ⊗ Δ[n]) _⦋d + 1⦌
hs₁ : s ∈ (Δ[m + 1] ⊗ Δ[n]).nonDegenerate (d + 1)
hs₂ : s ∉ (Λ[m + 1, k.castSucc].unionProd ∂Δ[n]).obj (Opposite.op ⦋d + 1⦌)
hs : IsIndex (Subcomplex.N.mk s hs₁ hs₂) ⋯ is.succ
t : (Δ[m + 1] ⊗ Δ[n]) _⦋d + 1⦌
ht₁ : t ∈ (Δ[m + 1] ⊗ Δ[n]).nonDegenerate (d + 1)
ht₂ : t ∉ (Λ[m + 1, k.castSucc].unionProd ∂Δ[n]).obj (Opposite.op ⦋d + 1⦌)
ht : IsIndex (Subcomplex.N.mk t ht₁ ht₂) ⋯ it.succ
h₂ :
  (pairingCore k n).type₂ { x := Subcomplex.N.mk s hs₁ hs₂, d := d, hd := ⋯, index := is, isIndex := hs } <
    (pairingCore k n).type₁ { x := Subcomplex.N.mk t ht₁ ht₂, d := d, hd := ⋯, index := it, isIndex := ht }
h₁ : ¬Subcomplex.N.mk s hs₁ hs₂ = Subcomplex.N.mk t ht₁ ht₂
i : Fin (d + 2)
hf : Mono (SimplexCategory.δ i)
hδ :
  (ConcreteCategory.hom ((Δ[m + 1] ⊗ Δ[n]).map (SimplexCategory.δ i).op))
      ((pairingCore k n).type₁
          { x := Subcomplex.N.mk t ht₁ ht₂, d := d, hd := ⋯, index := it, isIndex := ht }).simplex =
    ((pairingCore k n).type₂ { x := Subcomplex.N.mk s hs₁ hs₂, d := d, hd := ⋯, index := is, isIndex := hs }).simplex
⊢ { dim := hs.δ.dim, simplex := hs.δ.simplex } =
    { dim := d,
      simplex :=
        (ConcreteCategory.hom (SimplicialObject.δ (Δ[m + 1] ⊗ Δ[n]) i)) ((Subcomplex.N.mk t ht₁ ht₂).cast ⋯).simplex }

Tactic:
rw [S.ext_iff']

Goal state after:
m✝ : ℕ
k✝ : Fin (m✝ + 1)
n✝ : ℕ
x : (Λ[m✝ + 1, k✝.castSucc].unionProd ∂Δ[n✝]).N
d✝ m : ℕ
k : Fin (m + 1)
n d : ℕ
is it : Fin (d + 1)
s : (Δ[m + 1] ⊗ Δ[n]) _⦋d + 1⦌
hs₁ : s ∈ (Δ[m + 1] ⊗ Δ[n]).nonDegenerate (d + 1)
hs₂ : s ∉ (Λ[m + 1, k.castSucc].unionProd ∂Δ[n]).obj (Opposite.op ⦋d + 1⦌)
hs : IsIndex (Subcomplex.N.mk s hs₁ hs₂) ⋯ is.succ
t : (Δ[m + 1] ⊗ Δ[n]) _⦋d + 1⦌
ht₁ : t ∈ (Δ[m + 1] ⊗ Δ[n]).nonDegenerate (d + 1)
ht₂ : t ∉ (Λ[m + 1, k.castSucc].unionProd ∂Δ[n]).obj (Opposite.op ⦋d + 1⦌)
ht : IsIndex (Subcomplex.N.mk t ht₁ ht₂) ⋯ it.succ
h₂ :
  (pairingCore k n).type₂ { x := Subcomplex.N.mk s hs₁ hs₂, d := d, hd := ⋯, index := is, isIndex := hs } <
    (pairingCore k n).type₁ { x := Subcomplex.N.mk t ht₁ ht₂, d := d, hd := ⋯, index := it, isIndex := ht }
h₁ : ¬Subcomplex.N.mk s hs₁ hs₂ = Subcomplex.N.mk t ht₁ ht₂
i : Fin (d + 2)
hf : Mono (SimplexCategory.δ i)
hδ :
  (ConcreteCategory.hom ((Δ[m + 1] ⊗ Δ[n]).map (SimplexCategory.δ i).op))
      ((pairingCore k n).type₁
          { x := Subcomplex.N.mk t ht₁ ht₂, d := d, hd := ⋯, index := it, isIndex := ht }).simplex =
    ((pairingCore k n).type₂ { x := Subcomplex.N.mk s hs₁ hs₂, d := d, hd := ⋯, index := is, isIndex := hs }).simplex
⊢ ∃ (h :
    { dim := hs.δ.dim, simplex := hs.δ.simplex }.dim =
      { dim := d,
          simplex :=
            (ConcreteCategory.hom (SimplicialObject.δ (Δ[m + 1] ⊗ Δ[n]) i))
              ((Subcomplex.N.mk t ht₁ ht₂).cast ⋯).simplex }.dim),
    ({ dim := hs.δ.dim, simplex := hs.δ.simplex }.cast h).simplex =
      { dim := d,
          simplex :=
            (ConcreteCategory.hom (SimplicialObject.δ (Δ[m + 1] ⊗ Δ[n]) i))
              ((Subcomplex.N.mk t ht₁ ht₂).cast ⋯).simplex }.simplex