Theorem: MeasureTheory.lintegral_finset_sum'
File: Mathlib/MeasureTheory/Integral/Lebesgue.lean

tactic: induction' s using Finset.induction_on with a s has ih
state_before: α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
m : MeasurableSpace α
μ ν : Measure α
s : Finset β
f : β → α → ℝ≥0∞
hf : ∀ b ∈ s, AEMeasurable (f b) μ
⊢ ∫⁻ (a : α), ∑ b ∈ s, f b a ∂μ = ∑ b ∈ s, ∫⁻ (a : α), f b a ∂μ
state_after: case empty
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
m : MeasurableSpace α
μ ν : Measure α
f : β → α → ℝ≥0∞
hf : ∀ b ∈ ∅, AEMeasurable (f b) μ
⊢ ∫⁻ (a : α), ∑ b ∈ ∅, f b a ∂μ = ∑ b ∈ ∅, ∫⁻ (a : α), f b a ∂μ

case insert
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
m : MeasurableSpace α
μ ν : Measure α
f : β → α → ℝ≥0∞
a : β
s : Finset β
has : a ∉ s
ih : (∀ b ∈ s, AEMeasurable (f b) μ) → ∫⁻ (a : α), ∑ b ∈ s, f b a ∂μ = ∑ b ∈ s, ∫⁻ (a : α), f b a ∂μ
hf : ∀ b ∈ insert a s, AEMeasurable (f b) μ
⊢ ∫⁻ (a_1 : α), ∑ b ∈ insert a s, f b a_1 ∂μ = ∑ b ∈ insert a s, ∫⁻ (a : α), f b a ∂μ

tactic: simp
state_before: case empty
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
m : MeasurableSpace α
μ ν : Measure α
f : β → α → ℝ≥0∞
hf : ∀ b ∈ ∅, AEMeasurable (f b) μ
⊢ ∫⁻ (a : α), ∑ b ∈ ∅, f b a ∂μ = ∑ b ∈ ∅, ∫⁻ (a : α), f b a ∂μ
state_after: no goals

tactic: simp only [Finset.sum_insert has]
state_before: case insert
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
m : MeasurableSpace α
μ ν : Measure α
f : β → α → ℝ≥0∞
a : β
s : Finset β
has : a ∉ s
ih : (∀ b ∈ s, AEMeasurable (f b) μ) → ∫⁻ (a : α), ∑ b ∈ s, f b a ∂μ = ∑ b ∈ s, ∫⁻ (a : α), f b a ∂μ
hf : ∀ b ∈ insert a s, AEMeasurable (f b) μ
⊢ ∫⁻ (a_1 : α), ∑ b ∈ insert a s, f b a_1 ∂μ = ∑ b ∈ insert a s, ∫⁻ (a : α), f b a ∂μ
state_after: case insert
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
m : MeasurableSpace α
μ ν : Measure α
f : β → α → ℝ≥0∞
a : β
s : Finset β
has : a ∉ s
ih : (∀ b ∈ s, AEMeasurable (f b) μ) → ∫⁻ (a : α), ∑ b ∈ s, f b a ∂μ = ∑ b ∈ s, ∫⁻ (a : α), f b a ∂μ
hf : ∀ b ∈ insert a s, AEMeasurable (f b) μ
⊢ ∫⁻ (a_1 : α), f a a_1 + ∑ b ∈ s, f b a_1 ∂μ = ∫⁻ (a_1 : α), f a a_1 ∂μ + ∑ b ∈ s, ∫⁻ (a : α), f b a ∂μ

tactic: rw [Finset.forall_mem_insert] at hf
state_before: case insert
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
m : MeasurableSpace α
μ ν : Measure α
f : β → α → ℝ≥0∞
a : β
s : Finset β
has : a ∉ s
ih : (∀ b ∈ s, AEMeasurable (f b) μ) → ∫⁻ (a : α), ∑ b ∈ s, f b a ∂μ = ∑ b ∈ s, ∫⁻ (a : α), f b a ∂μ
hf : ∀ b ∈ insert a s, AEMeasurable (f b) μ
⊢ ∫⁻ (a_1 : α), f a a_1 + ∑ b ∈ s, f b a_1 ∂μ = ∫⁻ (a_1 : α), f a a_1 ∂μ + ∑ b ∈ s, ∫⁻ (a : α), f b a ∂μ
state_after: case insert
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
m : MeasurableSpace α
μ ν : Measure α
f : β → α → ℝ≥0∞
a : β
s : Finset β
has : a ∉ s
ih : (∀ b ∈ s, AEMeasurable (f b) μ) → ∫⁻ (a : α), ∑ b ∈ s, f b a ∂μ = ∑ b ∈ s, ∫⁻ (a : α), f b a ∂μ
hf : AEMeasurable (f a) μ ∧ ∀ x ∈ s, AEMeasurable (f x) μ
⊢ ∫⁻ (a_1 : α), f a a_1 + ∑ b ∈ s, f b a_1 ∂μ = ∫⁻ (a_1 : α), f a a_1 ∂μ + ∑ b ∈ s, ∫⁻ (a : α), f b a ∂μ

tactic: rw [lintegral_add_left' hf.1, ih hf.2]
state_before: case insert
α : Type u_1
β : Type u_2
γ : Type u_3
δ : Type u_4
m : MeasurableSpace α
μ ν : Measure α
f : β → α → ℝ≥0∞
a : β
s : Finset β
has : a ∉ s
ih : (∀ b ∈ s, AEMeasurable (f b) μ) → ∫⁻ (a : α), ∑ b ∈ s, f b a ∂μ = ∑ b ∈ s, ∫⁻ (a : α), f b a ∂μ
hf : AEMeasurable (f a) μ ∧ ∀ x ∈ s, AEMeasurable (f x) μ
⊢ ∫⁻ (a_1 : α), f a a_1 + ∑ b ∈ s, f b a_1 ∂μ = ∫⁻ (a_1 : α), f a a_1 ∂μ + ∑ b ∈ s, ∫⁻ (a : α), f b a ∂μ
state_after: no goals