Theorem: prod_generateFrom_generateFrom_eq
File: Mathlib/Topology/Constructions.lean

Proof steps:
state_before: X✝ : Type u
Y✝ : Type v
Z : Type u_1
W : Type u_2
ε : Type u_3
ζ : Type u_4
inst✝⁵ : TopologicalSpace X✝
inst✝⁴ : TopologicalSpace Y✝
inst✝³ : TopologicalSpace Z
inst✝² : TopologicalSpace W
inst✝¹ : TopologicalSpace ε
inst✝ : TopologicalSpace ζ
X : Type u_5
Y : Type u_6
s : Set (Set X)
t : Set (Set Y)
hs : ⋃₀ s = univ
ht : ⋃₀ t = univ
G : TopologicalSpace (X × Y) := generateFrom (image2 (fun x x_1 => x ×ˢ x_1) s t)
u : Set X
hu : u ∈ s
⊢ ⋃ v ∈ t, u ×ˢ v = Prod.fst ⁻¹' u
state_after: no goals
tactic: simp_rw [← prod_iUnion, ← sUnion_eq_biUnion, ht, prod_univ]
state_before: X✝ : Type u
Y✝ : Type v
Z : Type u_1
W : Type u_2
ε : Type u_3
ζ : Type u_4
inst✝⁵ : TopologicalSpace X✝
inst✝⁴ : TopologicalSpace Y✝
inst✝³ : TopologicalSpace Z
inst✝² : TopologicalSpace W
inst✝¹ : TopologicalSpace ε
inst✝ : TopologicalSpace ζ
X : Type u_5
Y : Type u_6
s : Set (Set X)
t : Set (Set Y)
hs : ⋃₀ s = univ
ht : ⋃₀ t = univ
G : TopologicalSpace (X × Y) := generateFrom (image2 (fun x x_1 => x ×ˢ x_1) s t)
u : Set X
hu : u ∈ s
this : ⋃ v ∈ t, u ×ˢ v = Prod.fst ⁻¹' u
⊢ TopologicalSpace.IsOpen (Prod.fst ⁻¹' u)
state_after: X✝ : Type u
Y✝ : Type v
Z : Type u_1
W : Type u_2
ε : Type u_3
ζ : Type u_4
inst✝⁵ : TopologicalSpace X✝
inst✝⁴ : TopologicalSpace Y✝
inst✝³ : TopologicalSpace Z
inst✝² : TopologicalSpace W
inst✝¹ : TopologicalSpace ε
inst✝ : TopologicalSpace ζ
X : Type u_5
Y : Type u_6
s : Set (Set X)
t : Set (Set Y)
hs : ⋃₀ s = univ
ht : ⋃₀ t = univ
G : TopologicalSpace (X × Y) := generateFrom (image2 (fun x x_1 => x ×ˢ x_1) s t)
u : Set X
hu : u ∈ s
this : ⋃ v ∈ t, u ×ˢ v = Prod.fst ⁻¹' u
⊢ TopologicalSpace.IsOpen (⋃ v ∈ t, u ×ˢ v)
tactic: rw [← this]
state_before: X✝ : Type u
Y✝ : Type v
Z : Type u_1
W : Type u_2
ε : Type u_3
ζ : Type u_4
inst✝⁵ : TopologicalSpace X✝
inst✝⁴ : TopologicalSpace Y✝
inst✝³ : TopologicalSpace Z
inst✝² : TopologicalSpace W
inst✝¹ : TopologicalSpace ε
inst✝ : TopologicalSpace ζ
X : Type u_5
Y : Type u_6
s : Set (Set X)
t : Set (Set Y)
hs : ⋃₀ s = univ
ht : ⋃₀ t = univ
G : TopologicalSpace (X × Y) := generateFrom (image2 (fun x x_1 => x ×ˢ x_1) s t)
u : Set X
hu : u ∈ s
this : ⋃ v ∈ t, u ×ˢ v = Prod.fst ⁻¹' u
⊢ TopologicalSpace.IsOpen (⋃ v ∈ t, u ×ˢ v)
state_after: no goals
tactic: exact
              isOpen_iUnion fun v =>
                isOpen_iUnion fun hv => GenerateOpen.basic _ ⟨_, hu, _, hv, rfl⟩
state_before: X✝ : Type u
Y✝ : Type v
Z : Type u_1
W : Type u_2
ε : Type u_3
ζ : Type u_4
inst✝⁵ : TopologicalSpace X✝
inst✝⁴ : TopologicalSpace Y✝
inst✝³ : TopologicalSpace Z
inst✝² : TopologicalSpace W
inst✝¹ : TopologicalSpace ε
inst✝ : TopologicalSpace ζ
X : Type u_5
Y : Type u_6
s : Set (Set X)
t : Set (Set Y)
hs : ⋃₀ s = univ
ht : ⋃₀ t = univ
G : TopologicalSpace (X × Y) := generateFrom (image2 (fun x x_1 => x ×ˢ x_1) s t)
v : Set Y
hv : v ∈ t
⊢ ⋃ u ∈ s, u ×ˢ v = Prod.snd ⁻¹' v
state_after: no goals
tactic: simp_rw [← iUnion_prod_const, ← sUnion_eq_biUnion, hs, univ_prod]
state_before: X✝ : Type u
Y✝ : Type v
Z : Type u_1
W : Type u_2
ε : Type u_3
ζ : Type u_4
inst✝⁵ : TopologicalSpace X✝
inst✝⁴ : TopologicalSpace Y✝
inst✝³ : TopologicalSpace Z
inst✝² : TopologicalSpace W
inst✝¹ : TopologicalSpace ε
inst✝ : TopologicalSpace ζ
X : Type u_5
Y : Type u_6
s : Set (Set X)
t : Set (Set Y)
hs : ⋃₀ s = univ
ht : ⋃₀ t = univ
G : TopologicalSpace (X × Y) := generateFrom (image2 (fun x x_1 => x ×ˢ x_1) s t)
v : Set Y
hv : v ∈ t
this : ⋃ u ∈ s, u ×ˢ v = Prod.snd ⁻¹' v
⊢ TopologicalSpace.IsOpen (Prod.snd ⁻¹' v)
state_after: X✝ : Type u
Y✝ : Type v
Z : Type u_1
W : Type u_2
ε : Type u_3
ζ : Type u_4
inst✝⁵ : TopologicalSpace X✝
inst✝⁴ : TopologicalSpace Y✝
inst✝³ : TopologicalSpace Z
inst✝² : TopologicalSpace W
inst✝¹ : TopologicalSpace ε
inst✝ : TopologicalSpace ζ
X : Type u_5
Y : Type u_6
s : Set (Set X)
t : Set (Set Y)
hs : ⋃₀ s = univ
ht : ⋃₀ t = univ
G : TopologicalSpace (X × Y) := generateFrom (image2 (fun x x_1 => x ×ˢ x_1) s t)
v : Set Y
hv : v ∈ t
this : ⋃ u ∈ s, u ×ˢ v = Prod.snd ⁻¹' v
⊢ TopologicalSpace.IsOpen (⋃ u ∈ s, u ×ˢ v)
tactic: rw [← this]
state_before: X✝ : Type u
Y✝ : Type v
Z : Type u_1
W : Type u_2
ε : Type u_3
ζ : Type u_4
inst✝⁵ : TopologicalSpace X✝
inst✝⁴ : TopologicalSpace Y✝
inst✝³ : TopologicalSpace Z
inst✝² : TopologicalSpace W
inst✝¹ : TopologicalSpace ε
inst✝ : TopologicalSpace ζ
X : Type u_5
Y : Type u_6
s : Set (Set X)
t : Set (Set Y)
hs : ⋃₀ s = univ
ht : ⋃₀ t = univ
G : TopologicalSpace (X × Y) := generateFrom (image2 (fun x x_1 => x ×ˢ x_1) s t)
v : Set Y
hv : v ∈ t
this : ⋃ u ∈ s, u ×ˢ v = Prod.snd ⁻¹' v
⊢ TopologicalSpace.IsOpen (⋃ u ∈ s, u ×ˢ v)
state_after: no goals
tactic: exact
              isOpen_iUnion fun u =>
                isOpen_iUnion fun hu => GenerateOpen.basic _ ⟨_, hu, _, hv, rfl⟩