-- Mathlib/Topology/UniformSpace/Ascoli.lean
theorem EquicontinuousOn.tendsto_uniformOnFun_iff_pi
    {𝔖 : Set (Set X)} (𝔖_compact : ∀ K ∈ 𝔖, IsCompact K) (𝔖_covers : ⋃₀ 𝔖 = univ)
    (F_eqcont : ∀ K ∈ 𝔖, EquicontinuousOn F K) (ℱ : Filter ι) (f : X → α) :
    Tendsto (UniformOnFun.ofFun 𝔖 ∘ F) ℱ (𝓝 <| UniformOnFun.ofFun 𝔖 f) ↔
    Tendsto F ℱ (𝓝 f)

Proof state:
ι : Type u_1
X : Type u_2
α : Type u_3
inst✝¹ : TopologicalSpace X
inst✝ : UniformSpace α
F : ι → X → α
𝔖 : Set (Set X)
𝔖_compact : ∀ K ∈ 𝔖, IsCompact K
𝔖_covers : ∀ (x : X), x ∈ ⋃₀ 𝔖
F_eqcont : ∀ K ∈ 𝔖, EquicontinuousOn F K
ℱ : Filter ι
f : X → α
φ : (↑(⋃₀ 𝔖) → α) ≃ₜ (X → α) := Homeomorph.piCongrLeft (Equiv.subtypeUnivEquiv 𝔖_covers)
⊢ (⋃₀ 𝔖).restrict ∘ F = ⇑φ.symm ∘ F

Tactic:
rfl

Result:
no goals

Proof state:
ι : Type u_1
X : Type u_2
α : Type u_3
inst✝¹ : TopologicalSpace X
inst✝ : UniformSpace α
F : ι → X → α
𝔖 : Set (Set X)
𝔖_compact : ∀ K ∈ 𝔖, IsCompact K
𝔖_covers : ∀ (x : X), x ∈ ⋃₀ 𝔖
F_eqcont : ∀ K ∈ 𝔖, EquicontinuousOn F K
ℱ : Filter ι
f : X → α
φ : (↑(⋃₀ 𝔖) → α) ≃ₜ (X → α) := Homeomorph.piCongrLeft (Equiv.subtypeUnivEquiv 𝔖_covers)
⊢ (⋃₀ 𝔖).restrict f = φ.symm f

Tactic:
rfl

Result:
no goals

Proof state:
ι : Type u_1
X : Type u_2
α : Type u_3
inst✝¹ : TopologicalSpace X
inst✝ : UniformSpace α
F : ι → X → α
𝔖 : Set (Set X)
𝔖_compact : ∀ K ∈ 𝔖, IsCompact K
𝔖_covers : ∀ (x : X), x ∈ ⋃₀ 𝔖
F_eqcont : ∀ K ∈ 𝔖, EquicontinuousOn F K
ℱ : Filter ι
f : X → α
⊢ Tendsto (⇑(UniformOnFun.ofFun 𝔖) ∘ F) ℱ (𝓝 ((UniformOnFun.ofFun 𝔖) f)) ↔ Tendsto F ℱ (𝓝 f)

Tactic:
let φ : ((⋃₀ 𝔖) → α) ≃ₜ (X → α) := Homeomorph.piCongrLeft (Y := fun _ ↦ α)
  (Equiv.subtypeUnivEquiv 𝔖_covers)

Result:
ι : Type u_1
X : Type u_2
α : Type u_3
inst✝¹ : TopologicalSpace X
inst✝ : UniformSpace α
F : ι → X → α
𝔖 : Set (Set X)
𝔖_compact : ∀ K ∈ 𝔖, IsCompact K
𝔖_covers : ∀ (x : X), x ∈ ⋃₀ 𝔖
F_eqcont : ∀ K ∈ 𝔖, EquicontinuousOn F K
ℱ : Filter ι
f : X → α
φ : (↑(⋃₀ 𝔖) → α) ≃ₜ (X → α) := Homeomorph.piCongrLeft (Equiv.subtypeUnivEquiv 𝔖_covers)
⊢ Tendsto (⇑(UniformOnFun.ofFun 𝔖) ∘ F) ℱ (𝓝 ((UniformOnFun.ofFun 𝔖) f)) ↔ Tendsto F ℱ (𝓝 f)

Proof state:
ι : Type u_1
X : Type u_2
α : Type u_3
inst✝¹ : TopologicalSpace X
inst✝ : UniformSpace α
F : ι → X → α
𝔖 : Set (Set X)
𝔖_compact : ∀ K ∈ 𝔖, IsCompact K
𝔖_covers : ∀ (x : X), x ∈ ⋃₀ 𝔖
F_eqcont : ∀ K ∈ 𝔖, EquicontinuousOn F K
ℱ : Filter ι
f : X → α
φ : (↑(⋃₀ 𝔖) → α) ≃ₜ (X → α) := Homeomorph.piCongrLeft (Equiv.subtypeUnivEquiv 𝔖_covers)
⊢ Tendsto (⇑(UniformOnFun.ofFun 𝔖) ∘ F) ℱ (𝓝 ((UniformOnFun.ofFun 𝔖) f)) ↔ Tendsto F ℱ (𝓝 f)

Tactic:
rw [EquicontinuousOn.tendsto_uniformOnFun_iff_pi' 𝔖_compact F_eqcont,
    show restrict (⋃₀ 𝔖) ∘ F = φ.symm ∘ F by rfl, show restrict (⋃₀ 𝔖) f = φ.symm f by rfl,
    φ.symm.isInducing.tendsto_nhds_iff]

Result:
no goals

Proof state:
ι : Type u_1
X : Type u_2
α : Type u_3
inst✝¹ : TopologicalSpace X
inst✝ : UniformSpace α
F : ι → X → α
𝔖 : Set (Set X)
𝔖_compact : ∀ K ∈ 𝔖, IsCompact K
𝔖_covers : ⋃₀ 𝔖 = univ
F_eqcont : ∀ K ∈ 𝔖, EquicontinuousOn F K
ℱ : Filter ι
f : X → α
⊢ Tendsto (⇑(UniformOnFun.ofFun 𝔖) ∘ F) ℱ (𝓝 ((UniformOnFun.ofFun 𝔖) f)) ↔ Tendsto F ℱ (𝓝 f)

Tactic:
rw [eq_univ_iff_forall] at 𝔖_covers

Result:
ι : Type u_1
X : Type u_2
α : Type u_3
inst✝¹ : TopologicalSpace X
inst✝ : UniformSpace α
F : ι → X → α
𝔖 : Set (Set X)
𝔖_compact : ∀ K ∈ 𝔖, IsCompact K
𝔖_covers : ∀ (x : X), x ∈ ⋃₀ 𝔖
F_eqcont : ∀ K ∈ 𝔖, EquicontinuousOn F K
ℱ : Filter ι
f : X → α
⊢ Tendsto (⇑(UniformOnFun.ofFun 𝔖) ∘ F) ℱ (𝓝 ((UniformOnFun.ofFun 𝔖) f)) ↔ Tendsto F ℱ (𝓝 f)