Theorem: measurableSet_prod_of_nonempty
File: Mathlib/MeasureTheory/MeasurableSpace/Basic.lean

tactic: rcases h with ⟨⟨x, y⟩, hx, hy⟩
state_before: α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
δ' : Type u_5
ι : Sort uι
s✝ t✝ u : Set α
m : MeasurableSpace α
mβ : MeasurableSpace β
mγ : MeasurableSpace γ
s : Set α
t : Set β
h : (s ×ˢ t).Nonempty
⊢ MeasurableSet (s ×ˢ t) ↔ MeasurableSet s ∧ MeasurableSet t
state_after: case intro.mk.intro
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
δ' : Type u_5
ι : Sort uι
s✝ t✝ u : Set α
m : MeasurableSpace α
mβ : MeasurableSpace β
mγ : MeasurableSpace γ
s : Set α
t : Set β
x : α
y : β
hx : (x, y).1 ∈ s
hy : (x, y).2 ∈ t
⊢ MeasurableSet (s ×ˢ t) ↔ MeasurableSet s ∧ MeasurableSet t

tactic: refine ⟨fun hst => ?_, fun h => h.1.prod h.2⟩
state_before: case intro.mk.intro
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
δ' : Type u_5
ι : Sort uι
s✝ t✝ u : Set α
m : MeasurableSpace α
mβ : MeasurableSpace β
mγ : MeasurableSpace γ
s : Set α
t : Set β
x : α
y : β
hx : (x, y).1 ∈ s
hy : (x, y).2 ∈ t
⊢ MeasurableSet (s ×ˢ t) ↔ MeasurableSet s ∧ MeasurableSet t
state_after: case intro.mk.intro
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
δ' : Type u_5
ι : Sort uι
s✝ t✝ u : Set α
m : MeasurableSpace α
mβ : MeasurableSpace β
mγ : MeasurableSpace γ
s : Set α
t : Set β
x : α
y : β
hx : (x, y).1 ∈ s
hy : (x, y).2 ∈ t
hst : MeasurableSet (s ×ˢ t)
⊢ MeasurableSet s ∧ MeasurableSet t

tactic: have : MeasurableSet ((fun x => (x, y)) ⁻¹' s ×ˢ t) := measurable_prod_mk_right hst
state_before: case intro.mk.intro
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
δ' : Type u_5
ι : Sort uι
s✝ t✝ u : Set α
m : MeasurableSpace α
mβ : MeasurableSpace β
mγ : MeasurableSpace γ
s : Set α
t : Set β
x : α
y : β
hx : (x, y).1 ∈ s
hy : (x, y).2 ∈ t
hst : MeasurableSet (s ×ˢ t)
⊢ MeasurableSet s ∧ MeasurableSet t
state_after: case intro.mk.intro
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
δ' : Type u_5
ι : Sort uι
s✝ t✝ u : Set α
m : MeasurableSpace α
mβ : MeasurableSpace β
mγ : MeasurableSpace γ
s : Set α
t : Set β
x : α
y : β
hx : (x, y).1 ∈ s
hy : (x, y).2 ∈ t
hst : MeasurableSet (s ×ˢ t)
this : MeasurableSet ((fun x => (x, y)) ⁻¹' s ×ˢ t)
⊢ MeasurableSet s ∧ MeasurableSet t

tactic: have : MeasurableSet (Prod.mk x ⁻¹' s ×ˢ t) := measurable_prod_mk_left hst
state_before: case intro.mk.intro
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
δ' : Type u_5
ι : Sort uι
s✝ t✝ u : Set α
m : MeasurableSpace α
mβ : MeasurableSpace β
mγ : MeasurableSpace γ
s : Set α
t : Set β
x : α
y : β
hx : (x, y).1 ∈ s
hy : (x, y).2 ∈ t
hst : MeasurableSet (s ×ˢ t)
this : MeasurableSet ((fun x => (x, y)) ⁻¹' s ×ˢ t)
⊢ MeasurableSet s ∧ MeasurableSet t
state_after: case intro.mk.intro
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
δ' : Type u_5
ι : Sort uι
s✝ t✝ u : Set α
m : MeasurableSpace α
mβ : MeasurableSpace β
mγ : MeasurableSpace γ
s : Set α
t : Set β
x : α
y : β
hx : (x, y).1 ∈ s
hy : (x, y).2 ∈ t
hst : MeasurableSet (s ×ˢ t)
this✝ : MeasurableSet ((fun x => (x, y)) ⁻¹' s ×ˢ t)
this : MeasurableSet (Prod.mk x ⁻¹' s ×ˢ t)
⊢ MeasurableSet s ∧ MeasurableSet t

tactic: simp_all
state_before: case intro.mk.intro
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
δ' : Type u_5
ι : Sort uι
s✝ t✝ u : Set α
m : MeasurableSpace α
mβ : MeasurableSpace β
mγ : MeasurableSpace γ
s : Set α
t : Set β
x : α
y : β
hx : (x, y).1 ∈ s
hy : (x, y).2 ∈ t
hst : MeasurableSet (s ×ˢ t)
this✝ : MeasurableSet ((fun x => (x, y)) ⁻¹' s ×ˢ t)
this : MeasurableSet (Prod.mk x ⁻¹' s ×ˢ t)
⊢ MeasurableSet s ∧ MeasurableSet t
state_after: no goals