Theorem: ProbabilityTheory.kernel.measurable_kernel_prod_mk_left'
File: Mathlib/Probability/Kernel/MeasurableIntegral.lean

tactic: have : ∀ b, Prod.mk b ⁻¹' s = {c | ((a, b), c) ∈ {p : (α × β) × γ | (p.1.2, p.2) ∈ s}} := by
  intro b; rfl
state_before: α : Type u_1
β : Type u_2
γ : Type u_3
mα : MeasurableSpace α
mβ : MeasurableSpace β
mγ : MeasurableSpace γ
κ : ↥(kernel α β)
η : ↥(kernel (α × β) γ)
a✝ : α
inst✝ : IsSFiniteKernel η
s : Set (β × γ)
hs : MeasurableSet s
a : α
⊢ Measurable fun b => (η (a, b)) (Prod.mk b ⁻¹' s)
state_after: α : Type u_1
β : Type u_2
γ : Type u_3
mα : MeasurableSpace α
mβ : MeasurableSpace β
mγ : MeasurableSpace γ
κ : ↥(kernel α β)
η : ↥(kernel (α × β) γ)
a✝ : α
inst✝ : IsSFiniteKernel η
s : Set (β × γ)
hs : MeasurableSet s
a : α
this : ∀ (b : β), Prod.mk b ⁻¹' s = {c | ((a, b), c) ∈ {p | (p.1.2, p.2) ∈ s}}
⊢ Measurable fun b => (η (a, b)) (Prod.mk b ⁻¹' s)

tactic: simp_rw [this]
state_before: α : Type u_1
β : Type u_2
γ : Type u_3
mα : MeasurableSpace α
mβ : MeasurableSpace β
mγ : MeasurableSpace γ
κ : ↥(kernel α β)
η : ↥(kernel (α × β) γ)
a✝ : α
inst✝ : IsSFiniteKernel η
s : Set (β × γ)
hs : MeasurableSet s
a : α
this : ∀ (b : β), Prod.mk b ⁻¹' s = {c | ((a, b), c) ∈ {p | (p.1.2, p.2) ∈ s}}
⊢ Measurable fun b => (η (a, b)) (Prod.mk b ⁻¹' s)
state_after: α : Type u_1
β : Type u_2
γ : Type u_3
mα : MeasurableSpace α
mβ : MeasurableSpace β
mγ : MeasurableSpace γ
κ : ↥(kernel α β)
η : ↥(kernel (α × β) γ)
a✝ : α
inst✝ : IsSFiniteKernel η
s : Set (β × γ)
hs : MeasurableSet s
a : α
this : ∀ (b : β), Prod.mk b ⁻¹' s = {c | ((a, b), c) ∈ {p | (p.1.2, p.2) ∈ s}}
⊢ Measurable fun b => (η (a, b)) {c | ((a, b), c) ∈ {p | (p.1.2, p.2) ∈ s}}

tactic: refine (measurable_kernel_prod_mk_left ?_).comp measurable_prod_mk_left
state_before: α : Type u_1
β : Type u_2
γ : Type u_3
mα : MeasurableSpace α
mβ : MeasurableSpace β
mγ : MeasurableSpace γ
κ : ↥(kernel α β)
η : ↥(kernel (α × β) γ)
a✝ : α
inst✝ : IsSFiniteKernel η
s : Set (β × γ)
hs : MeasurableSet s
a : α
this : ∀ (b : β), Prod.mk b ⁻¹' s = {c | ((a, b), c) ∈ {p | (p.1.2, p.2) ∈ s}}
⊢ Measurable fun b => (η (a, b)) {c | ((a, b), c) ∈ {p | (p.1.2, p.2) ∈ s}}
state_after: α : Type u_1
β : Type u_2
γ : Type u_3
mα : MeasurableSpace α
mβ : MeasurableSpace β
mγ : MeasurableSpace γ
κ : ↥(kernel α β)
η : ↥(kernel (α × β) γ)
a✝ : α
inst✝ : IsSFiniteKernel η
s : Set (β × γ)
hs : MeasurableSet s
a : α
this : ∀ (b : β), Prod.mk b ⁻¹' s = {c | ((a, b), c) ∈ {p | (p.1.2, p.2) ∈ s}}
⊢ MeasurableSet {p | (p.1.2, p.2) ∈ s}

tactic: exact (measurable_fst.snd.prod_mk measurable_snd) hs
state_before: α : Type u_1
β : Type u_2
γ : Type u_3
mα : MeasurableSpace α
mβ : MeasurableSpace β
mγ : MeasurableSpace γ
κ : ↥(kernel α β)
η : ↥(kernel (α × β) γ)
a✝ : α
inst✝ : IsSFiniteKernel η
s : Set (β × γ)
hs : MeasurableSet s
a : α
this : ∀ (b : β), Prod.mk b ⁻¹' s = {c | ((a, b), c) ∈ {p | (p.1.2, p.2) ∈ s}}
⊢ MeasurableSet {p | (p.1.2, p.2) ∈ s}
state_after: no goals

tactic: intro b
state_before: α : Type u_1
β : Type u_2
γ : Type u_3
mα : MeasurableSpace α
mβ : MeasurableSpace β
mγ : MeasurableSpace γ
κ : ↥(kernel α β)
η : ↥(kernel (α × β) γ)
a✝ : α
inst✝ : IsSFiniteKernel η
s : Set (β × γ)
hs : MeasurableSet s
a : α
⊢ ∀ (b : β), Prod.mk b ⁻¹' s = {c | ((a, b), c) ∈ {p | (p.1.2, p.2) ∈ s}}
state_after: α : Type u_1
β : Type u_2
γ : Type u_3
mα : MeasurableSpace α
mβ : MeasurableSpace β
mγ : MeasurableSpace γ
κ : ↥(kernel α β)
η : ↥(kernel (α × β) γ)
a✝ : α
inst✝ : IsSFiniteKernel η
s : Set (β × γ)
hs : MeasurableSet s
a : α
b : β
⊢ Prod.mk b ⁻¹' s = {c | ((a, b), c) ∈ {p | (p.1.2, p.2) ∈ s}}

tactic: rfl
state_before: α : Type u_1
β : Type u_2
γ : Type u_3
mα : MeasurableSpace α
mβ : MeasurableSpace β
mγ : MeasurableSpace γ
κ : ↥(kernel α β)
η : ↥(kernel (α × β) γ)
a✝ : α
inst✝ : IsSFiniteKernel η
s : Set (β × γ)
hs : MeasurableSet s
a : α
b : β
⊢ Prod.mk b ⁻¹' s = {c | ((a, b), c) ∈ {p | (p.1.2, p.2) ∈ s}}
state_after: no goals