Theorem: closure_image_mem_nhds_of_uniformInducing
File: Mathlib/Topology/UniformSpace/UniformEmbedding.lean

tactic: obtain ⟨U, ⟨hU, hUo, hsymm⟩, hs⟩ :
  ∃ U, (U ∈ 𝓤 β ∧ IsOpen U ∧ SymmetricRel U) ∧ Prod.map e e ⁻¹' U ⊆ s := by
    rwa [← he₁.comap_uniformity, (uniformity_hasBasis_open_symmetric.comap _).mem_iff] at hs
state_before: α : Type u
β : Type v
γ : Type w
inst✝² : UniformSpace α
inst✝¹ : UniformSpace β
inst✝ : UniformSpace γ
s : Set (α × α)
e : α → β
b : β
he₁ : UniformInducing e
he₂ : DenseInducing e
hs : s ∈ 𝓤 α
⊢ ∃ a, closure (e '' {a' | (a, a') ∈ s}) ∈ 𝓝 b

tactic: rcases he₂.dense.mem_nhds (UniformSpace.ball_mem_nhds b hU) with ⟨a, ha⟩
state_before: case intro.intro.intro.intro
α : Type u
β : Type v
γ : Type w
inst✝² : UniformSpace α
inst✝¹ : UniformSpace β
inst✝ : UniformSpace γ
s : Set (α × α)
e : α → β
b : β
he₁ : UniformInducing e
he₂ : DenseInducing e
hs✝ : s ∈ 𝓤 α
U : Set (β × β)
hs : Prod.map e e ⁻¹' U ⊆ s
hU : U ∈ 𝓤 β
hUo : IsOpen U
hsymm : SymmetricRel U
⊢ ∃ a, closure (e '' {a' | (a, a') ∈ s}) ∈ 𝓝 b

tactic: refine ⟨a, mem_of_superset ?_ (closure_mono <| image_subset _ <| ball_mono hs a)⟩
state_before: case intro.intro.intro.intro.intro
α : Type u
β : Type v
γ : Type w
inst✝² : UniformSpace α
inst✝¹ : UniformSpace β
inst✝ : UniformSpace γ
s : Set (α × α)
e : α → β
b : β
he₁ : UniformInducing e
he₂ : DenseInducing e
hs✝ : s ∈ 𝓤 α
U : Set (β × β)
hs : Prod.map e e ⁻¹' U ⊆ s
hU : U ∈ 𝓤 β
hUo : IsOpen U
hsymm : SymmetricRel U
a : α
ha : e a ∈ UniformSpace.ball b U
⊢ ∃ a, closure (e '' {a' | (a, a') ∈ s}) ∈ 𝓝 b

tactic: have ho : IsOpen (UniformSpace.ball (e a) U) := UniformSpace.isOpen_ball (e a) hUo
state_before: case intro.intro.intro.intro.intro
α : Type u
β : Type v
γ : Type w
inst✝² : UniformSpace α
inst✝¹ : UniformSpace β
inst✝ : UniformSpace γ
s : Set (α × α)
e : α → β
b : β
he₁ : UniformInducing e
he₂ : DenseInducing e
hs✝ : s ∈ 𝓤 α
U : Set (β × β)
hs : Prod.map e e ⁻¹' U ⊆ s
hU : U ∈ 𝓤 β
hUo : IsOpen U
hsymm : SymmetricRel U
a : α
ha : e a ∈ UniformSpace.ball b U
⊢ closure (e '' UniformSpace.ball a (Prod.map e e ⁻¹' U)) ∈ 𝓝 b

tactic: refine mem_of_superset (ho.mem_nhds <| (mem_ball_symmetry hsymm).2 ha) fun y hy => ?_
state_before: case intro.intro.intro.intro.intro
α : Type u
β : Type v
γ : Type w
inst✝² : UniformSpace α
inst✝¹ : UniformSpace β
inst✝ : UniformSpace γ
s : Set (α × α)
e : α → β
b : β
he₁ : UniformInducing e
he₂ : DenseInducing e
hs✝ : s ∈ 𝓤 α
U : Set (β × β)
hs : Prod.map e e ⁻¹' U ⊆ s
hU : U ∈ 𝓤 β
hUo : IsOpen U
hsymm : SymmetricRel U
a : α
ha : e a ∈ UniformSpace.ball b U
ho : IsOpen (UniformSpace.ball (e a) U)
⊢ closure (e '' UniformSpace.ball a (Prod.map e e ⁻¹' U)) ∈ 𝓝 b

tactic: refine mem_closure_iff_nhds.2 fun V hV => ?_
state_before: case intro.intro.intro.intro.intro
α : Type u
β : Type v
γ : Type w
inst✝² : UniformSpace α
inst✝¹ : UniformSpace β
inst✝ : UniformSpace γ
s : Set (α × α)
e : α → β
b : β
he₁ : UniformInducing e
he₂ : DenseInducing e
hs✝ : s ∈ 𝓤 α
U : Set (β × β)
hs : Prod.map e e ⁻¹' U ⊆ s
hU : U ∈ 𝓤 β
hUo : IsOpen U
hsymm : SymmetricRel U
a : α
ha : e a ∈ UniformSpace.ball b U
ho : IsOpen (UniformSpace.ball (e a) U)
y : β
hy : y ∈ UniformSpace.ball (e a) U
⊢ y ∈ closure (e '' UniformSpace.ball a (Prod.map e e ⁻¹' U))

tactic: rcases he₂.dense.mem_nhds (inter_mem hV (ho.mem_nhds hy)) with ⟨x, hxV, hxU⟩
state_before: case intro.intro.intro.intro.intro
α : Type u
β : Type v
γ : Type w
inst✝² : UniformSpace α
inst✝¹ : UniformSpace β
inst✝ : UniformSpace γ
s : Set (α × α)
e : α → β
b : β
he₁ : UniformInducing e
he₂ : DenseInducing e
hs✝ : s ∈ 𝓤 α
U : Set (β × β)
hs : Prod.map e e ⁻¹' U ⊆ s
hU : U ∈ 𝓤 β
hUo : IsOpen U
hsymm : SymmetricRel U
a : α
ha : e a ∈ UniformSpace.ball b U
ho : IsOpen (UniformSpace.ball (e a) U)
y : β
hy : y ∈ UniformSpace.ball (e a) U
V : Set β
hV : V ∈ 𝓝 y
⊢ Set.Nonempty (V ∩ e '' UniformSpace.ball a (Prod.map e e ⁻¹' U))

tactic: exact ⟨e x, hxV, mem_image_of_mem e hxU⟩
state_before: case intro.intro.intro.intro.intro.intro.intro
α : Type u
β : Type v
γ : Type w
inst✝² : UniformSpace α
inst✝¹ : UniformSpace β
inst✝ : UniformSpace γ
s : Set (α × α)
e : α → β
b : β
he₁ : UniformInducing e
he₂ : DenseInducing e
hs✝ : s ∈ 𝓤 α
U : Set (β × β)
hs : Prod.map e e ⁻¹' U ⊆ s
hU : U ∈ 𝓤 β
hUo : IsOpen U
hsymm : SymmetricRel U
a : α
ha : e a ∈ UniformSpace.ball b U
ho : IsOpen (UniformSpace.ball (e a) U)
y : β
hy : y ∈ UniformSpace.ball (e a) U
V : Set β
hV : V ∈ 𝓝 y
x : α
hxV : e x ∈ V
hxU : e x ∈ UniformSpace.ball (e a) U
⊢ Set.Nonempty (V ∩ e '' UniformSpace.ball a (Prod.map e e ⁻¹' U))

tactic: rwa [← he₁.comap_uniformity, (uniformity_hasBasis_open_symmetric.comap _).mem_iff] at hs
state_before: α : Type u
β : Type v
γ : Type w
inst✝² : UniformSpace α
inst✝¹ : UniformSpace β
inst✝ : UniformSpace γ
s : Set (α × α)
e : α → β
b : β
he₁ : UniformInducing e
he₂ : DenseInducing e
hs : s ∈ 𝓤 α
⊢ ∃ U, (U ∈ 𝓤 β ∧ IsOpen U ∧ SymmetricRel U) ∧ Prod.map e e ⁻¹' U ⊆ s