l3lab/ntp-mathlib huggingface dataset:
private theorem extend_Z_bilin_key (x₀ : α) (y₀ : γ) : ∃ U ∈ comap e (𝓝 x₀), ∃ V ∈ comap f (𝓝 y₀),
    ∀ (x) (_ : x ∈ U) (x') (_ : x' ∈ U), ∀ (y) (_ : y ∈ V) (y') (_ : y' ∈ V),
    (fun p : β × δ => φ p.1 p.2) (x', y') - (fun p : β × δ => φ p.1 p.2) (x, y) ∈ W' := by
  let ee := fun u : β × β => (e u.1, e u.2)
  let ff := fun u : δ × δ => (f u.1, f u.2)
  have lim_φ : Filter.Tendsto (fun p : β × δ => φ p.1 p.2) (𝓝 (0, 0)) (𝓝 0) := by
    simpa using hφ.tendsto (0, 0)
  have lim_φ_sub_sub :
    Tendsto (fun p : (β × β) × δ × δ => (fun p : β × δ => φ p.1 p.2) (p.1.2 - p.1.1, p.2.2 - p.2.1))
      ((comap ee <| 𝓝 (x₀, x₀)) ×ˢ (comap ff <| 𝓝 (y₀, y₀))) (𝓝 0) := by
    have lim_sub_sub :
      Tendsto (fun p : (β × β) × δ × δ => (p.1.2 - p.1.1, p.2.2 - p.2.1))
        (comap ee (𝓝 (x₀, x₀)) ×ˢ comap ff (𝓝 (y₀, y₀))) (𝓝 0 ×ˢ 𝓝 0) := by
      have := Filter.prod_mono (tendsto_sub_comap_self de x₀) (tendsto_sub_comap_self df y₀)
      rwa [prod_map_map_eq] at this
    rw [← nhds_prod_eq] at lim_sub_sub
    exact Tendsto.comp lim_φ lim_sub_sub
  rcases exists_nhds_zero_quarter W'_nhd with ⟨W, W_nhd, W4⟩
  have :
    ∃ U₁ ∈ comap e (𝓝 x₀), ∃ V₁ ∈ comap f (𝓝 y₀), ∀ (x) (_ : x ∈ U₁) (x') (_ : x' ∈ U₁),
      ∀ (y) (_ : y ∈ V₁) (y') (_ : y' ∈ V₁), (fun p : β × δ => φ p.1 p.2) (x' - x, y' - y) ∈ W := by
    rcases tendsto_prod_iff.1 lim_φ_sub_sub W W_nhd with ⟨U, U_in, V, V_in, H⟩
    rw [nhds_prod_eq, ← prod_comap_comap_eq, mem_prod_same_iff] at U_in V_in
    rcases U_in with ⟨U₁, U₁_in, HU₁⟩
    rcases V_in with ⟨V₁, V₁_in, HV₁⟩
    exists U₁, U₁_in, V₁, V₁_in
    intro x x_in x' x'_in y y_in y' y'_in
    exact H _ _ (HU₁ (mk_mem_prod x_in x'_in)) (HV₁ (mk_mem_prod y_in y'_in))
  

Proof state:
case intro.intro
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
G : Type u_5
inst✝¹⁶ : TopologicalSpace α
inst✝¹⁵ : AddCommGroup α
inst✝¹⁴ : TopologicalAddGroup α
inst✝¹³ : TopologicalSpace β
inst✝¹² : AddCommGroup β
inst✝¹¹ : TopologicalAddGroup β
inst✝¹⁰ : TopologicalSpace γ
inst✝⁹ : AddCommGroup γ
inst✝⁸ : TopologicalAddGroup γ
inst✝⁷ : TopologicalSpace δ
inst✝⁶ : AddCommGroup δ
inst✝⁵ : TopologicalAddGroup δ
inst✝⁴ : UniformSpace G
inst✝³ : AddCommGroup G
inst✝² : UniformAddGroup G
inst✝¹ : SeparatedSpace G
inst✝ : CompleteSpace G
e : β →+ α
de : DenseInducing ⇑e
f : δ →+ γ
df : DenseInducing ⇑f
φ : β →+ δ →+ G
hφ : Continuous fun p => (φ p.1) p.2
W' : Set G
W'_nhd : W' ∈ 𝓝 0
x₀ : α
y₀ : γ
ee : β × β → α × α := fun u => (e u.1, e u.2)
ff : δ × δ → γ × γ := fun u => (f u.1, f u.2)
lim_φ : Tendsto (fun p => (φ p.1) p.2) (𝓝 (0, 0)) (𝓝 0)
lim_φ_sub_sub :
  Tendsto (fun p => (fun p => (φ p.1) p.2) (p.1.2 - p.1.1, p.2.2 - p.2.1))
    (comap ee (𝓝 (x₀, x₀)) ×ˢ comap ff (𝓝 (y₀, y₀))) (𝓝 0)
W : Set G
W_nhd : W ∈ 𝓝 0
W4 : ∀ {v w s t : G}, v ∈ W → w ∈ W → s ∈ W → t ∈ W → v + w + s + t ∈ W'
this :
  ∃ U₁ ∈ comap (⇑e) (𝓝 x₀),
    ∃ V₁ ∈ comap (⇑f) (𝓝 y₀), ∀ x ∈ U₁, ∀ x' ∈ U₁, ∀ y ∈ V₁, ∀ y' ∈ V₁, (fun p => (φ p.1) p.2) (x' - x, y' - y) ∈ W
⊢ ∃ U ∈ comap (⇑e) (𝓝 x₀),
    ∃ V ∈ comap (⇑f) (𝓝 y₀),
      ∀ x ∈ U, ∀ x' ∈ U, ∀ y ∈ V, ∀ y' ∈ V, (fun p => (φ p.1) p.2) (x', y') - (fun p => (φ p.1) p.2) (x, y) ∈ W'

Next tactic:
rcases this with ⟨U₁, U₁_nhd, V₁, V₁_nhd, H⟩
/-- Bourbaki GT III.6.5 Theorem I:
ℤ-bilinear continuous maps from dense images into a complete Hausdorff group extend by continuity.
Note: Bourbaki assumes that α and β are also complete Hausdorff, but this is not necessary. -/
theorem extend_Z_bilin : Continuous (extend (de.prod df) (fun p : β × δ => φ p.1 p.2)) := by
  

Proof state:
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
G : Type u_5
inst✝¹⁶ : TopologicalSpace α
inst✝¹⁵ : AddCommGroup α
inst✝¹⁴ : TopologicalAddGroup α
inst✝¹³ : TopologicalSpace β
inst✝¹² : AddCommGroup β
inst✝¹¹ : TopologicalAddGroup β
inst✝¹⁰ : TopologicalSpace γ
inst✝⁹ : AddCommGroup γ
inst✝⁸ : TopologicalAddGroup γ
inst✝⁷ : TopologicalSpace δ
inst✝⁶ : AddCommGroup δ
inst✝⁵ : TopologicalAddGroup δ
inst✝⁴ : UniformSpace G
inst✝³ : AddCommGroup G
inst✝² : UniformAddGroup G
inst✝¹ : SeparatedSpace G
inst✝ : CompleteSpace G
e : β →+ α
de : DenseInducing ⇑e
f : δ →+ γ
df : DenseInducing ⇑f
φ : β →+ δ →+ G
hφ : Continuous fun p => (φ p.1) p.2
W' : Set G
W'_nhd : W' ∈ 𝓝 0
⊢ Continuous (extend (_ : DenseInducing fun p => (e p.1, f p.2)) fun p => (φ p.1) p.2)

Next tactic:
refine' continuous_extend_of_cauchy _ _
/-- Bourbaki GT III.6.5 Theorem I:
ℤ-bilinear continuous maps from dense images into a complete Hausdorff group extend by continuity.
Note: Bourbaki assumes that α and β are also complete Hausdorff, but this is not necessary. -/
theorem extend_Z_bilin : Continuous (extend (de.prod df) (fun p : β × δ => φ p.1 p.2)) := by
  refine' continuous_extend_of_cauchy _ _
  

Proof state:
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
G : Type u_5
inst✝¹⁶ : TopologicalSpace α
inst✝¹⁵ : AddCommGroup α
inst✝¹⁴ : TopologicalAddGroup α
inst✝¹³ : TopologicalSpace β
inst✝¹² : AddCommGroup β
inst✝¹¹ : TopologicalAddGroup β
inst✝¹⁰ : TopologicalSpace γ
inst✝⁹ : AddCommGroup γ
inst✝⁸ : TopologicalAddGroup γ
inst✝⁷ : TopologicalSpace δ
inst✝⁶ : AddCommGroup δ
inst✝⁵ : TopologicalAddGroup δ
inst✝⁴ : UniformSpace G
inst✝³ : AddCommGroup G
inst✝² : UniformAddGroup G
inst✝¹ : SeparatedSpace G
inst✝ : CompleteSpace G
e : β →+ α
de : DenseInducing ⇑e
f : δ →+ γ
df : DenseInducing ⇑f
φ : β →+ δ →+ G
hφ : Continuous fun p => (φ p.1) p.2
W' : Set G
W'_nhd : W' ∈ 𝓝 0
⊢ ∀ (b : α × γ), Cauchy (map (fun p => (φ p.1) p.2) (comap (fun p => (e p.1, f p.2)) (𝓝 b)))

Next tactic:
rintro ⟨x₀, y₀⟩
/-- Bourbaki GT III.6.5 Theorem I:
ℤ-bilinear continuous maps from dense images into a complete Hausdorff group extend by continuity.
Note: Bourbaki assumes that α and β are also complete Hausdorff, but this is not necessary. -/
theorem extend_Z_bilin : Continuous (extend (de.prod df) (fun p : β × δ => φ p.1 p.2)) := by
  refine' continuous_extend_of_cauchy _ _
  rintro ⟨x₀, y₀⟩
  

Proof state:
case mk
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
G : Type u_5
inst✝¹⁶ : TopologicalSpace α
inst✝¹⁵ : AddCommGroup α
inst✝¹⁴ : TopologicalAddGroup α
inst✝¹³ : TopologicalSpace β
inst✝¹² : AddCommGroup β
inst✝¹¹ : TopologicalAddGroup β
inst✝¹⁰ : TopologicalSpace γ
inst✝⁹ : AddCommGroup γ
inst✝⁸ : TopologicalAddGroup γ
inst✝⁷ : TopologicalSpace δ
inst✝⁶ : AddCommGroup δ
inst✝⁵ : TopologicalAddGroup δ
inst✝⁴ : UniformSpace G
inst✝³ : AddCommGroup G
inst✝² : UniformAddGroup G
inst✝¹ : SeparatedSpace G
inst✝ : CompleteSpace G
e : β →+ α
de : DenseInducing ⇑e
f : δ →+ γ
df : DenseInducing ⇑f
φ : β →+ δ →+ G
hφ : Continuous fun p => (φ p.1) p.2
W' : Set G
W'_nhd : W' ∈ 𝓝 0
x₀ : α
y₀ : γ
⊢ Cauchy (map (fun p => (φ p.1) p.2) (comap (fun p => (e p.1, f p.2)) (𝓝 (x₀, y₀))))

Next tactic:
constructor
/-- Bourbaki GT III.6.5 Theorem I:
ℤ-bilinear continuous maps from dense images into a complete Hausdorff group extend by continuity.
Note: Bourbaki assumes that α and β are also complete Hausdorff, but this is not necessary. -/
theorem extend_Z_bilin : Continuous (extend (de.prod df) (fun p : β × δ => φ p.1 p.2)) := by
  refine' continuous_extend_of_cauchy _ _
  rintro ⟨x₀, y₀⟩
  constructor
  · 

Proof state:
case mk.left
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
G : Type u_5
inst✝¹⁶ : TopologicalSpace α
inst✝¹⁵ : AddCommGroup α
inst✝¹⁴ : TopologicalAddGroup α
inst✝¹³ : TopologicalSpace β
inst✝¹² : AddCommGroup β
inst✝¹¹ : TopologicalAddGroup β
inst✝¹⁰ : TopologicalSpace γ
inst✝⁹ : AddCommGroup γ
inst✝⁸ : TopologicalAddGroup γ
inst✝⁷ : TopologicalSpace δ
inst✝⁶ : AddCommGroup δ
inst✝⁵ : TopologicalAddGroup δ
inst✝⁴ : UniformSpace G
inst✝³ : AddCommGroup G
inst✝² : UniformAddGroup G
inst✝¹ : SeparatedSpace G
inst✝ : CompleteSpace G
e : β →+ α
de : DenseInducing ⇑e
f : δ →+ γ
df : DenseInducing ⇑f
φ : β →+ δ →+ G
hφ : Continuous fun p => (φ p.1) p.2
W' : Set G
W'_nhd : W' ∈ 𝓝 0
x₀ : α
y₀ : γ
⊢ NeBot (map (fun p => (φ p.1) p.2) (comap (fun p => (e p.1, f p.2)) (𝓝 (x₀, y₀))))

Next tactic:
apply NeBot.map
/-- Bourbaki GT III.6.5 Theorem I:
ℤ-bilinear continuous maps from dense images into a complete Hausdorff group extend by continuity.
Note: Bourbaki assumes that α and β are also complete Hausdorff, but this is not necessary. -/
theorem extend_Z_bilin : Continuous (extend (de.prod df) (fun p : β × δ => φ p.1 p.2)) := by
  refine' continuous_extend_of_cauchy _ _
  rintro ⟨x₀, y₀⟩
  constructor
  · apply NeBot.map
    

Proof state:
case mk.left.hf
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
G : Type u_5
inst✝¹⁶ : TopologicalSpace α
inst✝¹⁵ : AddCommGroup α
inst✝¹⁴ : TopologicalAddGroup α
inst✝¹³ : TopologicalSpace β
inst✝¹² : AddCommGroup β
inst✝¹¹ : TopologicalAddGroup β
inst✝¹⁰ : TopologicalSpace γ
inst✝⁹ : AddCommGroup γ
inst✝⁸ : TopologicalAddGroup γ
inst✝⁷ : TopologicalSpace δ
inst✝⁶ : AddCommGroup δ
inst✝⁵ : TopologicalAddGroup δ
inst✝⁴ : UniformSpace G
inst✝³ : AddCommGroup G
inst✝² : UniformAddGroup G
inst✝¹ : SeparatedSpace G
inst✝ : CompleteSpace G
e : β →+ α
de : DenseInducing ⇑e
f : δ →+ γ
df : DenseInducing ⇑f
φ : β →+ δ →+ G
hφ : Continuous fun p => (φ p.1) p.2
W' : Set G
W'_nhd : W' ∈ 𝓝 0
x₀ : α
y₀ : γ
⊢ NeBot (comap (fun p => (e p.1, f p.2)) (𝓝 (x₀, y₀)))

Next tactic:
apply comap_neBot
/-- Bourbaki GT III.6.5 Theorem I:
ℤ-bilinear continuous maps from dense images into a complete Hausdorff group extend by continuity.
Note: Bourbaki assumes that α and β are also complete Hausdorff, but this is not necessary. -/
theorem extend_Z_bilin : Continuous (extend (de.prod df) (fun p : β × δ => φ p.1 p.2)) := by
  refine' continuous_extend_of_cauchy _ _
  rintro ⟨x₀, y₀⟩
  constructor
  · apply NeBot.map
    apply comap_neBot
    

Proof state:
case mk.left.hf.hm
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
G : Type u_5
inst✝¹⁶ : TopologicalSpace α
inst✝¹⁵ : AddCommGroup α
inst✝¹⁴ : TopologicalAddGroup α
inst✝¹³ : TopologicalSpace β
inst✝¹² : AddCommGroup β
inst✝¹¹ : TopologicalAddGroup β
inst✝¹⁰ : TopologicalSpace γ
inst✝⁹ : AddCommGroup γ
inst✝⁸ : TopologicalAddGroup γ
inst✝⁷ : TopologicalSpace δ
inst✝⁶ : AddCommGroup δ
inst✝⁵ : TopologicalAddGroup δ
inst✝⁴ : UniformSpace G
inst✝³ : AddCommGroup G
inst✝² : UniformAddGroup G
inst✝¹ : SeparatedSpace G
inst✝ : CompleteSpace G
e : β →+ α
de : DenseInducing ⇑e
f : δ →+ γ
df : DenseInducing ⇑f
φ : β →+ δ →+ G
hφ : Continuous fun p => (φ p.1) p.2
W' : Set G
W'_nhd : W' ∈ 𝓝 0
x₀ : α
y₀ : γ
⊢ ∀ t ∈ 𝓝 (x₀, y₀), ∃ a, (e a.1, f a.2) ∈ t

Next tactic:
intro U h
/-- Bourbaki GT III.6.5 Theorem I:
ℤ-bilinear continuous maps from dense images into a complete Hausdorff group extend by continuity.
Note: Bourbaki assumes that α and β are also complete Hausdorff, but this is not necessary. -/
theorem extend_Z_bilin : Continuous (extend (de.prod df) (fun p : β × δ => φ p.1 p.2)) := by
  refine' continuous_extend_of_cauchy _ _
  rintro ⟨x₀, y₀⟩
  constructor
  · apply NeBot.map
    apply comap_neBot
    intro U h
    

Proof state:
case mk.left.hf.hm
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
G : Type u_5
inst✝¹⁶ : TopologicalSpace α
inst✝¹⁵ : AddCommGroup α
inst✝¹⁴ : TopologicalAddGroup α
inst✝¹³ : TopologicalSpace β
inst✝¹² : AddCommGroup β
inst✝¹¹ : TopologicalAddGroup β
inst✝¹⁰ : TopologicalSpace γ
inst✝⁹ : AddCommGroup γ
inst✝⁸ : TopologicalAddGroup γ
inst✝⁷ : TopologicalSpace δ
inst✝⁶ : AddCommGroup δ
inst✝⁵ : TopologicalAddGroup δ
inst✝⁴ : UniformSpace G
inst✝³ : AddCommGroup G
inst✝² : UniformAddGroup G
inst✝¹ : SeparatedSpace G
inst✝ : CompleteSpace G
e : β →+ α
de : DenseInducing ⇑e
f : δ →+ γ
df : DenseInducing ⇑f
φ : β →+ δ →+ G
hφ : Continuous fun p => (φ p.1) p.2
W' : Set G
W'_nhd : W' ∈ 𝓝 0
x₀ : α
y₀ : γ
U : Set (α × γ)
h : U ∈ 𝓝 (x₀, y₀)
⊢ ∃ a, (e a.1, f a.2) ∈ U

Next tactic:
rcases mem_closure_iff_nhds.1 ((de.prod df).dense (x₀, y₀)) U h with ⟨x, x_in, ⟨z, z_x⟩⟩
/-- Bourbaki GT III.6.5 Theorem I:
ℤ-bilinear continuous maps from dense images into a complete Hausdorff group extend by continuity.
Note: Bourbaki assumes that α and β are also complete Hausdorff, but this is not necessary. -/
theorem extend_Z_bilin : Continuous (extend (de.prod df) (fun p : β × δ => φ p.1 p.2)) := by
  refine' continuous_extend_of_cauchy _ _
  rintro ⟨x₀, y₀⟩
  constructor
  · apply NeBot.map
    apply comap_neBot
    intro U h
    rcases mem_closure_iff_nhds.1 ((de.prod df).dense (x₀, y₀)) U h with ⟨x, x_in, ⟨z, z_x⟩⟩
    

Proof state:
case mk.left.hf.hm.intro.intro.intro
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
G : Type u_5
inst✝¹⁶ : TopologicalSpace α
inst✝¹⁵ : AddCommGroup α
inst✝¹⁴ : TopologicalAddGroup α
inst✝¹³ : TopologicalSpace β
inst✝¹² : AddCommGroup β
inst✝¹¹ : TopologicalAddGroup β
inst✝¹⁰ : TopologicalSpace γ
inst✝⁹ : AddCommGroup γ
inst✝⁸ : TopologicalAddGroup γ
inst✝⁷ : TopologicalSpace δ
inst✝⁶ : AddCommGroup δ
inst✝⁵ : TopologicalAddGroup δ
inst✝⁴ : UniformSpace G
inst✝³ : AddCommGroup G
inst✝² : UniformAddGroup G
inst✝¹ : SeparatedSpace G
inst✝ : CompleteSpace G
e : β →+ α
de : DenseInducing ⇑e
f : δ →+ γ
df : DenseInducing ⇑f
φ : β →+ δ →+ G
hφ : Continuous fun p => (φ p.1) p.2
W' : Set G
W'_nhd : W' ∈ 𝓝 0
x₀ : α
y₀ : γ
U : Set (α × γ)
h : U ∈ 𝓝 (x₀, y₀)
x : α × γ
x_in : x ∈ U
z : β × δ
z_x : (fun p => (e p.1, f p.2)) z = x
⊢ ∃ a, (e a.1, f a.2) ∈ U

Next tactic:
exists z
/-- Bourbaki GT III.6.5 Theorem I:
ℤ-bilinear continuous maps from dense images into a complete Hausdorff group extend by continuity.
Note: Bourbaki assumes that α and β are also complete Hausdorff, but this is not necessary. -/
theorem extend_Z_bilin : Continuous (extend (de.prod df) (fun p : β × δ => φ p.1 p.2)) := by
  refine' continuous_extend_of_cauchy _ _
  rintro ⟨x₀, y₀⟩
  constructor
  · apply NeBot.map
    apply comap_neBot
    intro U h
    rcases mem_closure_iff_nhds.1 ((de.prod df).dense (x₀, y₀)) U h with ⟨x, x_in, ⟨z, z_x⟩⟩
    exists z
    

Proof state:
case mk.left.hf.hm.intro.intro.intro
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
G : Type u_5
inst✝¹⁶ : TopologicalSpace α
inst✝¹⁵ : AddCommGroup α
inst✝¹⁴ : TopologicalAddGroup α
inst✝¹³ : TopologicalSpace β
inst✝¹² : AddCommGroup β
inst✝¹¹ : TopologicalAddGroup β
inst✝¹⁰ : TopologicalSpace γ
inst✝⁹ : AddCommGroup γ
inst✝⁸ : TopologicalAddGroup γ
inst✝⁷ : TopologicalSpace δ
inst✝⁶ : AddCommGroup δ
inst✝⁵ : TopologicalAddGroup δ
inst✝⁴ : UniformSpace G
inst✝³ : AddCommGroup G
inst✝² : UniformAddGroup G
inst✝¹ : SeparatedSpace G
inst✝ : CompleteSpace G
e : β →+ α
de : DenseInducing ⇑e
f : δ →+ γ
df : DenseInducing ⇑f
φ : β →+ δ →+ G
hφ : Continuous fun p => (φ p.1) p.2
W' : Set G
W'_nhd : W' ∈ 𝓝 0
x₀ : α
y₀ : γ
U : Set (α × γ)
h : U ∈ 𝓝 (x₀, y₀)
x : α × γ
x_in : x ∈ U
z : β × δ
z_x : (fun p => (e p.1, f p.2)) z = x
⊢ (e z.1, f z.2) ∈ U

Next tactic:
aesop
/-- Bourbaki GT III.6.5 Theorem I:
ℤ-bilinear continuous maps from dense images into a complete Hausdorff group extend by continuity.
Note: Bourbaki assumes that α and β are also complete Hausdorff, but this is not necessary. -/
theorem extend_Z_bilin : Continuous (extend (de.prod df) (fun p : β × δ => φ p.1 p.2)) := by
  refine' continuous_extend_of_cauchy _ _
  rintro ⟨x₀, y₀⟩
  constructor
  · apply NeBot.map
    apply comap_neBot
    intro U h
    rcases mem_closure_iff_nhds.1 ((de.prod df).dense (x₀, y₀)) U h with ⟨x, x_in, ⟨z, z_x⟩⟩
    exists z
    aesop
  · 

Proof state:
case mk.right
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
G : Type u_5
inst✝¹⁶ : TopologicalSpace α
inst✝¹⁵ : AddCommGroup α
inst✝¹⁴ : TopologicalAddGroup α
inst✝¹³ : TopologicalSpace β
inst✝¹² : AddCommGroup β
inst✝¹¹ : TopologicalAddGroup β
inst✝¹⁰ : TopologicalSpace γ
inst✝⁹ : AddCommGroup γ
inst✝⁸ : TopologicalAddGroup γ
inst✝⁷ : TopologicalSpace δ
inst✝⁶ : AddCommGroup δ
inst✝⁵ : TopologicalAddGroup δ
inst✝⁴ : UniformSpace G
inst✝³ : AddCommGroup G
inst✝² : UniformAddGroup G
inst✝¹ : SeparatedSpace G
inst✝ : CompleteSpace G
e : β →+ α
de : DenseInducing ⇑e
f : δ →+ γ
df : DenseInducing ⇑f
φ : β →+ δ →+ G
hφ : Continuous fun p => (φ p.1) p.2
W' : Set G
W'_nhd : W' ∈ 𝓝 0
x₀ : α
y₀ : γ
⊢ map (fun p => (φ p.1) p.2) (comap (fun p => (e p.1, f p.2)) (𝓝 (x₀, y₀))) ×ˢ
      map (fun p => (φ p.1) p.2) (comap (fun p => (e p.1, f p.2)) (𝓝 (x₀, y₀))) ≤
    𝓤 G

Next tactic:
suffices map (fun p : (β × δ) × β × δ => (fun p : β × δ => φ p.1 p.2) p.2 -
      (fun p : β × δ => φ p.1 p.2) p.1)
        (comap (fun p : (β × δ) × β × δ => ((e p.1.1, f p.1.2), (e p.2.1, f p.2.2)))
        (𝓝 (x₀, y₀) ×ˢ 𝓝 (x₀, y₀))) ≤ 𝓝 0 by
      rwa [uniformity_eq_comap_nhds_zero G, prod_map_map_eq, ← map_le_iff_le_comap, Filter.map_map,
        prod_comap_comap_eq]
/-- Bourbaki GT III.6.5 Theorem I:
ℤ-bilinear continuous maps from dense images into a complete Hausdorff group extend by continuity.
Note: Bourbaki assumes that α and β are also complete Hausdorff, but this is not necessary. -/
theorem extend_Z_bilin : Continuous (extend (de.prod df) (fun p : β × δ => φ p.1 p.2)) := by
  refine' continuous_extend_of_cauchy _ _
  rintro ⟨x₀, y₀⟩
  constructor
  · apply NeBot.map
    apply comap_neBot
    intro U h
    rcases mem_closure_iff_nhds.1 ((de.prod df).dense (x₀, y₀)) U h with ⟨x, x_in, ⟨z, z_x⟩⟩
    exists z
    aesop
  · suffices map (fun p : (β × δ) × β × δ => (fun p : β × δ => φ p.1 p.2) p.2 -
      (fun p : β × δ => φ p.1 p.2) p.1)
        (comap (fun p : (β × δ) × β × δ => ((e p.1.1, f p.1.2), (e p.2.1, f p.2.2)))
        (𝓝 (x₀, y₀) ×ˢ 𝓝 (x₀, y₀))) ≤ 𝓝 0 by
      

Proof state:
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
G : Type u_5
inst✝¹⁶ : TopologicalSpace α
inst✝¹⁵ : AddCommGroup α
inst✝¹⁴ : TopologicalAddGroup α
inst✝¹³ : TopologicalSpace β
inst✝¹² : AddCommGroup β
inst✝¹¹ : TopologicalAddGroup β
inst✝¹⁰ : TopologicalSpace γ
inst✝⁹ : AddCommGroup γ
inst✝⁸ : TopologicalAddGroup γ
inst✝⁷ : TopologicalSpace δ
inst✝⁶ : AddCommGroup δ
inst✝⁵ : TopologicalAddGroup δ
inst✝⁴ : UniformSpace G
inst✝³ : AddCommGroup G
inst✝² : UniformAddGroup G
inst✝¹ : SeparatedSpace G
inst✝ : CompleteSpace G
e : β →+ α
de : DenseInducing ⇑e
f : δ →+ γ
df : DenseInducing ⇑f
φ : β →+ δ →+ G
hφ : Continuous fun p => (φ p.1) p.2
W' : Set G
W'_nhd : W' ∈ 𝓝 0
x₀ : α
y₀ : γ
this :
  map (fun p => (fun p => (φ p.1) p.2) p.2 - (fun p => (φ p.1) p.2) p.1)
      (comap (fun p => ((e p.1.1, f p.1.2), e p.2.1, f p.2.2)) (𝓝 (x₀, y₀) ×ˢ 𝓝 (x₀, y₀))) ≤
    𝓝 0
⊢ map (fun p => (φ p.1) p.2) (comap (fun p => (e p.1, f p.2)) (𝓝 (x₀, y₀))) ×ˢ
      map (fun p => (φ p.1) p.2) (comap (fun p => (e p.1, f p.2)) (𝓝 (x₀, y₀))) ≤
    𝓤 G

Next tactic:
rwa [uniformity_eq_comap_nhds_zero G, prod_map_map_eq, ← map_le_iff_le_comap, Filter.map_map,
        prod_comap_comap_eq]
/-- Bourbaki GT III.6.5 Theorem I:
ℤ-bilinear continuous maps from dense images into a complete Hausdorff group extend by continuity.
Note: Bourbaki assumes that α and β are also complete Hausdorff, but this is not necessary. -/
theorem extend_Z_bilin : Continuous (extend (de.prod df) (fun p : β × δ => φ p.1 p.2)) := by
  refine' continuous_extend_of_cauchy _ _
  rintro ⟨x₀, y₀⟩
  constructor
  · apply NeBot.map
    apply comap_neBot
    intro U h
    rcases mem_closure_iff_nhds.1 ((de.prod df).dense (x₀, y₀)) U h with ⟨x, x_in, ⟨z, z_x⟩⟩
    exists z
    aesop
  · suffices map (fun p : (β × δ) × β × δ => (fun p : β × δ => φ p.1 p.2) p.2 -
      (fun p : β × δ => φ p.1 p.2) p.1)
        (comap (fun p : (β × δ) × β × δ => ((e p.1.1, f p.1.2), (e p.2.1, f p.2.2)))
        (𝓝 (x₀, y₀) ×ˢ 𝓝 (x₀, y₀))) ≤ 𝓝 0 by
      rwa [uniformity_eq_comap_nhds_zero G, prod_map_map_eq, ← map_le_iff_le_comap, Filter.map_map,
        prod_comap_comap_eq]
    

Proof state:
case mk.right
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
G : Type u_5
inst✝¹⁶ : TopologicalSpace α
inst✝¹⁵ : AddCommGroup α
inst✝¹⁴ : TopologicalAddGroup α
inst✝¹³ : TopologicalSpace β
inst✝¹² : AddCommGroup β
inst✝¹¹ : TopologicalAddGroup β
inst✝¹⁰ : TopologicalSpace γ
inst✝⁹ : AddCommGroup γ
inst✝⁸ : TopologicalAddGroup γ
inst✝⁷ : TopologicalSpace δ
inst✝⁶ : AddCommGroup δ
inst✝⁵ : TopologicalAddGroup δ
inst✝⁴ : UniformSpace G
inst✝³ : AddCommGroup G
inst✝² : UniformAddGroup G
inst✝¹ : SeparatedSpace G
inst✝ : CompleteSpace G
e : β →+ α
de : DenseInducing ⇑e
f : δ →+ γ
df : DenseInducing ⇑f
φ : β →+ δ →+ G
hφ : Continuous fun p => (φ p.1) p.2
W' : Set G
W'_nhd : W' ∈ 𝓝 0
x₀ : α
y₀ : γ
⊢ map (fun p => (fun p => (φ p.1) p.2) p.2 - (fun p => (φ p.1) p.2) p.1)
      (comap (fun p => ((e p.1.1, f p.1.2), e p.2.1, f p.2.2)) (𝓝 (x₀, y₀) ×ˢ 𝓝 (x₀, y₀))) ≤
    𝓝 0

Next tactic:
intro W' W'_nhd
/-- Bourbaki GT III.6.5 Theorem I:
ℤ-bilinear continuous maps from dense images into a complete Hausdorff group extend by continuity.
Note: Bourbaki assumes that α and β are also complete Hausdorff, but this is not necessary. -/
theorem extend_Z_bilin : Continuous (extend (de.prod df) (fun p : β × δ => φ p.1 p.2)) := by
  refine' continuous_extend_of_cauchy _ _
  rintro ⟨x₀, y₀⟩
  constructor
  · apply NeBot.map
    apply comap_neBot
    intro U h
    rcases mem_closure_iff_nhds.1 ((de.prod df).dense (x₀, y₀)) U h with ⟨x, x_in, ⟨z, z_x⟩⟩
    exists z
    aesop
  · suffices map (fun p : (β × δ) × β × δ => (fun p : β × δ => φ p.1 p.2) p.2 -
      (fun p : β × δ => φ p.1 p.2) p.1)
        (comap (fun p : (β × δ) × β × δ => ((e p.1.1, f p.1.2), (e p.2.1, f p.2.2)))
        (𝓝 (x₀, y₀) ×ˢ 𝓝 (x₀, y₀))) ≤ 𝓝 0 by
      rwa [uniformity_eq_comap_nhds_zero G, prod_map_map_eq, ← map_le_iff_le_comap, Filter.map_map,
        prod_comap_comap_eq]
    intro W' W'_nhd
    

Proof state:
case mk.right
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
G : Type u_5
inst✝¹⁶ : TopologicalSpace α
inst✝¹⁵ : AddCommGroup α
inst✝¹⁴ : TopologicalAddGroup α
inst✝¹³ : TopologicalSpace β
inst✝¹² : AddCommGroup β
inst✝¹¹ : TopologicalAddGroup β
inst✝¹⁰ : TopologicalSpace γ
inst✝⁹ : AddCommGroup γ
inst✝⁸ : TopologicalAddGroup γ
inst✝⁷ : TopologicalSpace δ
inst✝⁶ : AddCommGroup δ
inst✝⁵ : TopologicalAddGroup δ
inst✝⁴ : UniformSpace G
inst✝³ : AddCommGroup G
inst✝² : UniformAddGroup G
inst✝¹ : SeparatedSpace G
inst✝ : CompleteSpace G
e : β →+ α
de : DenseInducing ⇑e
f : δ →+ γ
df : DenseInducing ⇑f
φ : β →+ δ →+ G
hφ : Continuous fun p => (φ p.1) p.2
W'✝ : Set G
W'_nhd✝ : W'✝ ∈ 𝓝 0
x₀ : α
y₀ : γ
W' : Set G
W'_nhd : W' ∈ 𝓝 0
⊢ W' ∈
    map (fun p => (fun p => (φ p.1) p.2) p.2 - (fun p => (φ p.1) p.2) p.1)
      (comap (fun p => ((e p.1.1, f p.1.2), e p.2.1, f p.2.2)) (𝓝 (x₀, y₀) ×ˢ 𝓝 (x₀, y₀)))

Next tactic:
have key := extend_Z_bilin_key de df hφ W'_nhd x₀ y₀