-- Mathlib/Analysis/FunctionalSpaces/SobolevInequality.lean
theorem T_insert_le_T_lmarginal_singleton [∀ i, SigmaFinite (μ i)] (hp₀ : 0 ≤ p) (s : Finset ι)
    (hp : (s.card : ℝ) * p ≤ 1)
    (i : ι) (hi : i ∉ s) {f : (∀ i, A i) → ℝ≥0∞} (hf : Measurable f) :
    T μ p f (insert i s) ≤ T μ p (∫⋯∫⁻_{i}, f ∂μ) s

Proof state:
case h.e'_4.h
ι : Type u_1
A : ι → Type u_2
inst✝² : (i : ι) → MeasurableSpace (A i)
μ : (i : ι) → Measure (A i)
inst✝¹ : DecidableEq ι
p : ℝ
inst✝ : ∀ (i : ι), SigmaFinite (μ i)
hp₀ : 0 ≤ p
s : Finset ι
hp : ↑(#s) * p ≤ 1
i : ι
hi : i ∉ s
f : ((i : ι) → A i) → ℝ≥0∞
hf : Measurable f
x : (i : ι) → A i
k : ℝ := ↑(#s)
hk' : 0 ≤ 1 - k * p
X : A i → (a : ι) → A a
hF₁ : ∀ {j : ι}, Measurable fun t => (∫⋯∫⁻_{j}, f ∂μ) (X t)
hF₀ : Measurable fun t => f (X t)
t : A i
⊢ f (X t) ^ (1 - k * p) * ∏ j ∈ insert i s, (∫⋯∫⁻_{j}, f ∂μ) (X t) ^ p =
    (∫⋯∫⁻_{i}, f ∂μ) (X t) ^ p * (f (X t) ^ (1 - k * p) * ∏ j ∈ s, (∫⋯∫⁻_{j}, f ∂μ) (X t) ^ p)

Tactic:
simp_rw [prod_insert hi]

Result:
case h.e'_4.h
ι : Type u_1
A : ι → Type u_2
inst✝² : (i : ι) → MeasurableSpace (A i)
μ : (i : ι) → Measure (A i)
inst✝¹ : DecidableEq ι
p : ℝ
inst✝ : ∀ (i : ι), SigmaFinite (μ i)
hp₀ : 0 ≤ p
s : Finset ι
hp : ↑(#s) * p ≤ 1
i : ι
hi : i ∉ s
f : ((i : ι) → A i) → ℝ≥0∞
hf : Measurable f
x : (i : ι) → A i
k : ℝ := ↑(#s)
hk' : 0 ≤ 1 - k * p
X : A i → (a : ι) → A a
hF₁ : ∀ {j : ι}, Measurable fun t => (∫⋯∫⁻_{j}, f ∂μ) (X t)
hF₀ : Measurable fun t => f (X t)
t : A i
⊢ f (X t) ^ (1 - k * p) * ((∫⋯∫⁻_{i}, f ∂μ) (X t) ^ p * ∏ j ∈ s, (∫⋯∫⁻_{j}, f ∂μ) (X t) ^ p) =
    (∫⋯∫⁻_{i}, f ∂μ) (X t) ^ p * (f (X t) ^ (1 - k * p) * ∏ j ∈ s, (∫⋯∫⁻_{j}, f ∂μ) (X t) ^ p)

Proof state:
case bc.hf
ι : Type u_1
A : ι → Type u_2
inst✝² : (i : ι) → MeasurableSpace (A i)
μ : (i : ι) → Measure (A i)
inst✝¹ : DecidableEq ι
p : ℝ
inst✝ : ∀ (i : ι), SigmaFinite (μ i)
hp₀ : 0 ≤ p
s : Finset ι
hp : ↑(#s) * p ≤ 1
i : ι
hi : i ∉ s
f : ((i : ι) → A i) → ℝ≥0∞
hf : Measurable f
x : (i : ι) → A i
X : A i → (a : ι) → A a := update x i
hF₁ : ∀ {j : ι}, Measurable fun t => (∫⋯∫⁻_{j}, f ∂μ) (X t)
hF₀ : Measurable fun t => f (X t)
k : ℝ := ↑(#s)
hk' : 0 ≤ 1 - k * p
i✝ : ι
a✝ : i✝ ∈ s
⊢ AEMeasurable (fun a => (∫⋯∫⁻_{i✝}, f ∂μ) (X a)) (μ i)

Tactic:
exact hF₁.aemeasurable

Result:
no goals

Proof state:
ι : Type u_1
A : ι → Type u_2
inst✝² : (i : ι) → MeasurableSpace (A i)
μ : (i : ι) → Measure (A i)
inst✝¹ : DecidableEq ι
p : ℝ
inst✝ : ∀ (i : ι), SigmaFinite (μ i)
hp₀ : 0 ≤ p
s : Finset ι
hp : ↑(#s) * p ≤ 1
i : ι
hi : i ∉ s
f : ((i : ι) → A i) → ℝ≥0∞
hf : Measurable f
⊢ T μ p f (insert i s) = ∫⋯∫⁻_insert i s, f ^ (1 - ↑(#s) * p) * ∏ j ∈ insert i s, (∫⋯∫⁻_{j}, f ∂μ) ^ p ∂μ

Tactic:
simp_rw [T, card_insert_of_not_mem hi]

Result:
ι : Type u_1
A : ι → Type u_2
inst✝² : (i : ι) → MeasurableSpace (A i)
μ : (i : ι) → Measure (A i)
inst✝¹ : DecidableEq ι
p : ℝ
inst✝ : ∀ (i : ι), SigmaFinite (μ i)
hp₀ : 0 ≤ p
s : Finset ι
hp : ↑(#s) * p ≤ 1
i : ι
hi : i ∉ s
f : ((i : ι) → A i) → ℝ≥0∞
hf : Measurable f
⊢ ∫⋯∫⁻_insert i s, f ^ (1 - (↑(#s + 1) - 1) * p) * ∏ i ∈ insert i s, (∫⋯∫⁻_{i}, f ∂μ) ^ p ∂μ =
    ∫⋯∫⁻_insert i s, f ^ (1 - ↑(#s) * p) * ∏ i ∈ insert i s, (∫⋯∫⁻_{i}, f ∂μ) ^ p ∂μ

Proof state:
ι : Type u_1
A : ι → Type u_2
inst✝² : (i : ι) → MeasurableSpace (A i)
μ : (i : ι) → Measure (A i)
inst✝¹ : DecidableEq ι
p : ℝ
inst✝ : ∀ (i : ι), SigmaFinite (μ i)
hp₀ : 0 ≤ p
s : Finset ι
hp : ↑(#s) * p ≤ 1
i : ι
hi : i ∉ s
f : ((i : ι) → A i) → ℝ≥0∞
hf : Measurable f
x : (i : ι) → A i
X : A i → (a : ι) → A a := update x i
hF₁ : ∀ {j : ι}, Measurable fun t => (∫⋯∫⁻_{j}, f ∂μ) (X t)
hF₀ : Measurable fun t => f (X t)
⊢ ∫⁻ (t : A i), f (X t) ^ (1 - ↑(#s) * p) * ∏ j ∈ insert i s, (∫⋯∫⁻_{j}, f ∂μ) (X t) ^ p ∂μ i ≤
    (∫⋯∫⁻_{i}, f ∂μ) x ^ (1 - (↑(#s) - 1) * p) * ∏ x_1 ∈ s, (∫⋯∫⁻_{x_1}, ∫⋯∫⁻_{i}, f ∂μ ∂μ) x ^ p

Tactic:
let k : ℝ := s.card

Result:
ι : Type u_1
A : ι → Type u_2
inst✝² : (i : ι) → MeasurableSpace (A i)
μ : (i : ι) → Measure (A i)
inst✝¹ : DecidableEq ι
p : ℝ
inst✝ : ∀ (i : ι), SigmaFinite (μ i)
hp₀ : 0 ≤ p
s : Finset ι
hp : ↑(#s) * p ≤ 1
i : ι
hi : i ∉ s
f : ((i : ι) → A i) → ℝ≥0∞
hf : Measurable f
x : (i : ι) → A i
X : A i → (a : ι) → A a := update x i
hF₁ : ∀ {j : ι}, Measurable fun t => (∫⋯∫⁻_{j}, f ∂μ) (X t)
hF₀ : Measurable fun t => f (X t)
k : ℝ := ↑(#s)
⊢ ∫⁻ (t : A i), f (X t) ^ (1 - ↑(#s) * p) * ∏ j ∈ insert i s, (∫⋯∫⁻_{j}, f ∂μ) (X t) ^ p ∂μ i ≤
    (∫⋯∫⁻_{i}, f ∂μ) x ^ (1 - (↑(#s) - 1) * p) * ∏ x_1 ∈ s, (∫⋯∫⁻_{x_1}, ∫⋯∫⁻_{i}, f ∂μ ∂μ) x ^ p

Proof state:
case hy
ι : Type u_1
A : ι → Type u_2
inst✝² : (i : ι) → MeasurableSpace (A i)
μ : (i : ι) → Measure (A i)
inst✝¹ : DecidableEq ι
p : ℝ
inst✝ : ∀ (i : ι), SigmaFinite (μ i)
hp₀ : 0 ≤ p
s : Finset ι
hp : ↑(#s) * p ≤ 1
i : ι
hi : i ∉ s
f : ((i : ι) → A i) → ℝ≥0∞
hf : Measurable f
x : (i : ι) → A i
X : A i → (a : ι) → A a := update x i
hF₁ : ∀ {j : ι}, Measurable fun t => (∫⋯∫⁻_{j}, f ∂μ) (X t)
hF₀ : Measurable fun t => f (X t)
k : ℝ := ↑(#s)
hk' : 0 ≤ 1 - k * p
⊢ 0 ≤ p

Tactic:
exact hp₀

Result:
no goals

Proof state:
case hz
ι : Type u_1
A : ι → Type u_2
inst✝² : (i : ι) → MeasurableSpace (A i)
μ : (i : ι) → Measure (A i)
inst✝¹ : DecidableEq ι
p : ℝ
inst✝ : ∀ (i : ι), SigmaFinite (μ i)
hp₀ : 0 ≤ p
s : Finset ι
hp : ↑(#s) * p ≤ 1
i : ι
hi : i ∉ s
f : ((i : ι) → A i) → ℝ≥0∞
hf : Measurable f
x : (i : ι) → A i
X : A i → (a : ι) → A a := update x i
hF₁ : ∀ {j : ι}, Measurable fun t => (∫⋯∫⁻_{j}, f ∂μ) (X t)
hF₀ : Measurable fun t => f (X t)
k : ℝ := ↑(#s)
hk' : 0 ≤ 1 - k * p
⊢ 0 ≤ 1 - k * p

Tactic:
exact hk'

Result:
no goals

Proof state:
case hxy.h.e'_5.h.e'_6
ι : Type u_1
A : ι → Type u_2
inst✝² : (i : ι) → MeasurableSpace (A i)
μ : (i : ι) → Measure (A i)
inst✝¹ : DecidableEq ι
p : ℝ
inst✝ : ∀ (i : ι), SigmaFinite (μ i)
hp₀ : 0 ≤ p
s : Finset ι
hp : ↑(#s) * p ≤ 1
i : ι
hi : i ∉ s
f : ((i : ι) → A i) → ℝ≥0∞
hf : Measurable f
x : (i : ι) → A i
X : A i → (a : ι) → A a := update x i
hF₁ : ∀ {j : ι}, Measurable fun t => (∫⋯∫⁻_{j}, f ∂μ) (X t)
hF₀ : Measurable fun t => f (X t)
k : ℝ := ↑(#s)
hk' : 0 ≤ 1 - k * p
⊢ p + (1 - k * p) = 1 - (↑(#s) - 1) * p

Tactic:
ring_nf

Result:
no goals

Proof state:
ι : Type u_1
A : ι → Type u_2
inst✝² : (i : ι) → MeasurableSpace (A i)
μ : (i : ι) → Measure (A i)
inst✝¹ : DecidableEq ι
p : ℝ
inst✝ : ∀ (i : ι), SigmaFinite (μ i)
hp₀ : 0 ≤ p
s : Finset ι
hp : ↑(#s) * p ≤ 1
i : ι
hi : i ∉ s
f : ((i : ι) → A i) → ℝ≥0∞
hf : Measurable f
x : (i : ι) → A i
X : A i → (a : ι) → A a := update x i
hF₁ : ∀ {j : ι}, Measurable fun t => (∫⋯∫⁻_{j}, f ∂μ) (X t)
hF₀ : Measurable fun t => f (X t)
k : ℝ := ↑(#s)
hk' : 0 ≤ 1 - k * p
⊢ (∫⋯∫⁻_{i}, f ∂μ) x ^ p * ∫⁻ (t : A i), f (X t) ^ (1 - k * p) * ∏ j ∈ s, (∫⋯∫⁻_{j}, f ∂μ) (X t) ^ p ∂μ i ≤
    (∫⋯∫⁻_{i}, f ∂μ) x ^ p *
      ((∫⁻ (t : A i), f (X t) ∂μ i) ^ (1 - k * p) * ∏ j ∈ s, (∫⁻ (t : A i), (∫⋯∫⁻_{j}, f ∂μ) (X t) ∂μ i) ^ p)

Tactic:
gcongr

Result:
case bc
ι : Type u_1
A : ι → Type u_2
inst✝² : (i : ι) → MeasurableSpace (A i)
μ : (i : ι) → Measure (A i)
inst✝¹ : DecidableEq ι
p : ℝ
inst✝ : ∀ (i : ι), SigmaFinite (μ i)
hp₀ : 0 ≤ p
s : Finset ι
hp : ↑(#s) * p ≤ 1
i : ι
hi : i ∉ s
f : ((i : ι) → A i) → ℝ≥0∞
hf : Measurable f
x : (i : ι) → A i
X : A i → (a : ι) → A a := update x i
hF₁ : ∀ {j : ι}, Measurable fun t => (∫⋯∫⁻_{j}, f ∂μ) (X t)
hF₀ : Measurable fun t => f (X t)
k : ℝ := ↑(#s)
hk' : 0 ≤ 1 - k * p
⊢ ∫⁻ (t : A i), f (X t) ^ (1 - k * p) * ∏ j ∈ s, (∫⋯∫⁻_{j}, f ∂μ) (X t) ^ p ∂μ i ≤
    (∫⁻ (t : A i), f (X t) ∂μ i) ^ (1 - k * p) * ∏ j ∈ s, (∫⁻ (t : A i), (∫⋯∫⁻_{j}, f ∂μ) (X t) ∂μ i) ^ p