-- Mathlib/Topology/MetricSpace/GromovHausdorff.lean
theorem ghDist_le_hausdorffDist {X : Type u} [MetricSpace X] [CompactSpace X] [Nonempty X]
    {Y : Type v} [MetricSpace Y] [CompactSpace Y] [Nonempty Y] {γ : Type w} [MetricSpace γ]
    {Φ : X → γ} {Ψ : Y → γ} (ha : Isometry Φ) (hb : Isometry Ψ) :
    ghDist X Y ≤ hausdorffDist (range Φ) (range Ψ)

Proof state:
X : Type u
inst✝⁶ : MetricSpace X
inst✝⁵ : CompactSpace X
inst✝⁴ : Nonempty X
Y : Type v
inst✝³ : MetricSpace Y
inst✝² : CompactSpace Y
inst✝¹ : Nonempty Y
γ : Type w
inst✝ : MetricSpace γ
Φ : X → γ
Ψ : Y → γ
ha : Isometry Φ
hb : Isometry Ψ
xX : X
h✝ : xX ∈ univ
s : Set γ := range Φ ∪ range Ψ
Φ' : X → Subtype s := fun y => ⟨Φ y, ⋯⟩
Ψ' : Y → Subtype s := fun y => ⟨Ψ y, ⋯⟩
IΦ' : Isometry Φ'
IΨ' : Isometry Ψ'
this✝⁴ : IsCompact s
this✝³ : MetricSpace (Subtype s) := inferInstance
this✝² : CompactSpace (Subtype s)
this✝¹ : Nonempty (Subtype s)
ΦΦ' : Φ = Subtype.val ∘ Φ'
ΨΨ' : Ψ = Subtype.val ∘ Ψ'
this✝ : hausdorffDist (range Φ) (range Ψ) = hausdorffDist (range Φ') (range Ψ')
F : Subtype s → ↥(lp (fun i => ℝ) ⊤) := kuratowskiEmbedding (Subtype s)
this : hausdorffDist (F '' range Φ') (F '' range Ψ') = hausdorffDist (range Φ') (range Ψ')
A : NonemptyCompacts ↥(lp (fun n => ℝ) ⊤) := { carrier := F '' range Φ', isCompact' := ⋯, nonempty' := ⋯ }
B : NonemptyCompacts ↥(lp (fun n => ℝ) ⊤) := { carrier := F '' range Ψ', isCompact' := ⋯, nonempty' := ⋯ }
⊢ ⟦A⟧ = toGHSpace X

Tactic:
rw [eq_toGHSpace_iff]

Result:
X : Type u
inst✝⁶ : MetricSpace X
inst✝⁵ : CompactSpace X
inst✝⁴ : Nonempty X
Y : Type v
inst✝³ : MetricSpace Y
inst✝² : CompactSpace Y
inst✝¹ : Nonempty Y
γ : Type w
inst✝ : MetricSpace γ
Φ : X → γ
Ψ : Y → γ
ha : Isometry Φ
hb : Isometry Ψ
xX : X
h✝ : xX ∈ univ
s : Set γ := range Φ ∪ range Ψ
Φ' : X → Subtype s := fun y => ⟨Φ y, ⋯⟩
Ψ' : Y → Subtype s := fun y => ⟨Ψ y, ⋯⟩
IΦ' : Isometry Φ'
IΨ' : Isometry Ψ'
this✝⁴ : IsCompact s
this✝³ : MetricSpace (Subtype s) := inferInstance
this✝² : CompactSpace (Subtype s)
this✝¹ : Nonempty (Subtype s)
ΦΦ' : Φ = Subtype.val ∘ Φ'
ΨΨ' : Ψ = Subtype.val ∘ Ψ'
this✝ : hausdorffDist (range Φ) (range Ψ) = hausdorffDist (range Φ') (range Ψ')
F : Subtype s → ↥(lp (fun i => ℝ) ⊤) := kuratowskiEmbedding (Subtype s)
this : hausdorffDist (F '' range Φ') (F '' range Ψ') = hausdorffDist (range Φ') (range Ψ')
A : NonemptyCompacts ↥(lp (fun n => ℝ) ⊤) := { carrier := F '' range Φ', isCompact' := ⋯, nonempty' := ⋯ }
B : NonemptyCompacts ↥(lp (fun n => ℝ) ⊤) := { carrier := F '' range Ψ', isCompact' := ⋯, nonempty' := ⋯ }
⊢ ∃ Ψ, Isometry Ψ ∧ range Ψ = ↑A

Proof state:
case intro.refine_2
X : Type u
inst✝⁶ : MetricSpace X
inst✝⁵ : CompactSpace X
inst✝⁴ : Nonempty X
Y : Type v
inst✝³ : MetricSpace Y
inst✝² : CompactSpace Y
inst✝¹ : Nonempty Y
γ : Type w
inst✝ : MetricSpace γ
Φ : X → γ
Ψ : Y → γ
ha : Isometry Φ
hb : Isometry Ψ
xX : X
h✝ : xX ∈ univ
s : Set γ := range Φ ∪ range Ψ
Φ' : X → Subtype s := fun y => ⟨Φ y, ⋯⟩
Ψ' : Y → Subtype s := fun y => ⟨Ψ y, ⋯⟩
IΦ' : Isometry Φ'
IΨ' : Isometry Ψ'
this✝⁴ : IsCompact s
this✝³ : MetricSpace (Subtype s) := inferInstance
this✝² : CompactSpace (Subtype s)
this✝¹ : Nonempty (Subtype s)
ΦΦ' : Φ = Subtype.val ∘ Φ'
ΨΨ' : Ψ = Subtype.val ∘ Ψ'
this✝ : hausdorffDist (range Φ) (range Ψ) = hausdorffDist (range Φ') (range Ψ')
F : Subtype s → ↥(lp (fun i => ℝ) ⊤) := kuratowskiEmbedding (Subtype s)
this : hausdorffDist (F '' range Φ') (F '' range Ψ') = hausdorffDist (range Φ') (range Ψ')
A : NonemptyCompacts ↥(lp (fun n => ℝ) ⊤) := { carrier := F '' range Φ', isCompact' := ⋯, nonempty' := ⋯ }
B : NonemptyCompacts ↥(lp (fun n => ℝ) ⊤) := { carrier := F '' range Ψ', isCompact' := ⋯, nonempty' := ⋯ }
AX : ⟦A⟧ = toGHSpace X
BY : ⟦B⟧ = toGHSpace Y
⊢ hausdorffDist (F '' range Φ') (F '' range Ψ') ∈
    (fun p => hausdorffDist ↑p.1 ↑p.2) '' {a | ⟦a⟧ = toGHSpace X} ×ˢ {b | ⟦b⟧ = toGHSpace Y}

Tactic:
apply (mem_image _ _ _).2

Result:
case intro.refine_2
X : Type u
inst✝⁶ : MetricSpace X
inst✝⁵ : CompactSpace X
inst✝⁴ : Nonempty X
Y : Type v
inst✝³ : MetricSpace Y
inst✝² : CompactSpace Y
inst✝¹ : Nonempty Y
γ : Type w
inst✝ : MetricSpace γ
Φ : X → γ
Ψ : Y → γ
ha : Isometry Φ
hb : Isometry Ψ
xX : X
h✝ : xX ∈ univ
s : Set γ := range Φ ∪ range Ψ
Φ' : X → Subtype s := fun y => ⟨Φ y, ⋯⟩
Ψ' : Y → Subtype s := fun y => ⟨Ψ y, ⋯⟩
IΦ' : Isometry Φ'
IΨ' : Isometry Ψ'
this✝⁴ : IsCompact s
this✝³ : MetricSpace (Subtype s) := inferInstance
this✝² : CompactSpace (Subtype s)
this✝¹ : Nonempty (Subtype s)
ΦΦ' : Φ = Subtype.val ∘ Φ'
ΨΨ' : Ψ = Subtype.val ∘ Ψ'
this✝ : hausdorffDist (range Φ) (range Ψ) = hausdorffDist (range Φ') (range Ψ')
F : Subtype s → ↥(lp (fun i => ℝ) ⊤) := kuratowskiEmbedding (Subtype s)
this : hausdorffDist (F '' range Φ') (F '' range Ψ') = hausdorffDist (range Φ') (range Ψ')
A : NonemptyCompacts ↥(lp (fun n => ℝ) ⊤) := { carrier := F '' range Φ', isCompact' := ⋯, nonempty' := ⋯ }
B : NonemptyCompacts ↥(lp (fun n => ℝ) ⊤) := { carrier := F '' range Ψ', isCompact' := ⋯, nonempty' := ⋯ }
AX : ⟦A⟧ = toGHSpace X
BY : ⟦B⟧ = toGHSpace Y
⊢ ∃ x ∈ {a | ⟦a⟧ = toGHSpace X} ×ˢ {b | ⟦b⟧ = toGHSpace Y},
    hausdorffDist ↑x.1 ↑x.2 = hausdorffDist (F '' range Φ') (F '' range Ψ')

Proof state:
X : Type u
inst✝⁶ : MetricSpace X
inst✝⁵ : CompactSpace X
inst✝⁴ : Nonempty X
Y : Type v
inst✝³ : MetricSpace Y
inst✝² : CompactSpace Y
inst✝¹ : Nonempty Y
γ : Type w
inst✝ : MetricSpace γ
Φ : X → γ
Ψ : Y → γ
ha : Isometry Φ
hb : Isometry Ψ
xX : X
h✝ : xX ∈ univ
s : Set γ := range Φ ∪ range Ψ
Φ' : X → Subtype s := fun y => ⟨Φ y, ⋯⟩
Ψ' : Y → Subtype s := fun y => ⟨Ψ y, ⋯⟩
IΦ' : Isometry Φ'
IΨ' : Isometry Ψ'
this✝² : IsCompact s
this✝¹ : MetricSpace (Subtype s) := inferInstance
this✝ : CompactSpace (Subtype s)
this : Nonempty (Subtype s)
ΦΦ' : Φ = Subtype.val ∘ Φ'
ΨΨ' : Ψ = Subtype.val ∘ Ψ'
⊢ hausdorffDist (range Φ) (range Ψ) = hausdorffDist (range Φ') (range Ψ')

Tactic:
rw [ΦΦ', ΨΨ', range_comp, range_comp]

Result:
X : Type u
inst✝⁶ : MetricSpace X
inst✝⁵ : CompactSpace X
inst✝⁴ : Nonempty X
Y : Type v
inst✝³ : MetricSpace Y
inst✝² : CompactSpace Y
inst✝¹ : Nonempty Y
γ : Type w
inst✝ : MetricSpace γ
Φ : X → γ
Ψ : Y → γ
ha : Isometry Φ
hb : Isometry Ψ
xX : X
h✝ : xX ∈ univ
s : Set γ := range Φ ∪ range Ψ
Φ' : X → Subtype s := fun y => ⟨Φ y, ⋯⟩
Ψ' : Y → Subtype s := fun y => ⟨Ψ y, ⋯⟩
IΦ' : Isometry Φ'
IΨ' : Isometry Ψ'
this✝² : IsCompact s
this✝¹ : MetricSpace (Subtype s) := inferInstance
this✝ : CompactSpace (Subtype s)
this : Nonempty (Subtype s)
ΦΦ' : Φ = Subtype.val ∘ Φ'
ΨΨ' : Ψ = Subtype.val ∘ Ψ'
⊢ hausdorffDist (Subtype.val '' range Φ') (Subtype.val '' range Ψ') = hausdorffDist (range Φ') (range Ψ')