-- Mathlib/MeasureTheory/Measure/Haar/Unique.lean
/-- **Uniqueness of left-invariant measures**:
Given two left-invariant measures which are finite
on compacts and inner regular, they coincide up to a multiplicative constant. -/
@[to_additive isAddLeftInvariant_eq_smul_of_innerRegular]
lemma isMulLeftInvariant_eq_smul_of_innerRegular [LocallyCompactSpace G]
    (μ' μ : Measure G) [IsHaarMeasure μ] [IsFiniteMeasureOnCompacts μ'] [IsMulLeftInvariant μ']
    [InnerRegular μ] [InnerRegular μ'] :
    μ' = haarScalarFactor μ' μ • μ

Proof state:
case h.h.e'_4.h.f.f
G : Type u_1
inst✝¹⁰ : TopologicalSpace G
inst✝⁹ : Group G
inst✝⁸ : IsTopologicalGroup G
inst✝⁷ : MeasurableSpace G
inst✝⁶ : BorelSpace G
inst✝⁵ : LocallyCompactSpace G
μ' μ : Measure G
inst✝⁴ : μ.IsHaarMeasure
inst✝³ : IsFiniteMeasureOnCompacts μ'
inst✝² : μ'.IsMulLeftInvariant
inst✝¹ : μ.InnerRegular
inst✝ : μ'.InnerRegular
s : Set G
hs : MeasurableSet s
K : Set G
_Ks : K ⊆ s
K_comp : IsCompact K
⊢ μ' K = (μ'.haarScalarFactor μ • μ) K

Tactic:
exact measure_isMulLeftInvariant_eq_smul_of_ne_top μ' μ K_comp.measure_lt_top.ne
  K_comp.measure_lt_top.ne

Result:
no goals

Proof state:
G : Type u_1
inst✝¹⁰ : TopologicalSpace G
inst✝⁹ : Group G
inst✝⁸ : IsTopologicalGroup G
inst✝⁷ : MeasurableSpace G
inst✝⁶ : BorelSpace G
inst✝⁵ : LocallyCompactSpace G
μ' μ : Measure G
inst✝⁴ : μ.IsHaarMeasure
inst✝³ : IsFiniteMeasureOnCompacts μ'
inst✝² : μ'.IsMulLeftInvariant
inst✝¹ : μ.InnerRegular
inst✝ : μ'.InnerRegular
⊢ μ' = μ'.haarScalarFactor μ • μ

Tactic:
ext s hs

Result:
case h
G : Type u_1
inst✝¹⁰ : TopologicalSpace G
inst✝⁹ : Group G
inst✝⁸ : IsTopologicalGroup G
inst✝⁷ : MeasurableSpace G
inst✝⁶ : BorelSpace G
inst✝⁵ : LocallyCompactSpace G
μ' μ : Measure G
inst✝⁴ : μ.IsHaarMeasure
inst✝³ : IsFiniteMeasureOnCompacts μ'
inst✝² : μ'.IsMulLeftInvariant
inst✝¹ : μ.InnerRegular
inst✝ : μ'.InnerRegular
s : Set G
hs : MeasurableSet s
⊢ μ' s = (μ'.haarScalarFactor μ • μ) s

Proof state:
case h
G : Type u_1
inst✝¹⁰ : TopologicalSpace G
inst✝⁹ : Group G
inst✝⁸ : IsTopologicalGroup G
inst✝⁷ : MeasurableSpace G
inst✝⁶ : BorelSpace G
inst✝⁵ : LocallyCompactSpace G
μ' μ : Measure G
inst✝⁴ : μ.IsHaarMeasure
inst✝³ : IsFiniteMeasureOnCompacts μ'
inst✝² : μ'.IsMulLeftInvariant
inst✝¹ : μ.InnerRegular
inst✝ : μ'.InnerRegular
s : Set G
hs : MeasurableSet s
⊢ μ' s = (μ'.haarScalarFactor μ • μ) s

Tactic:
rw [hs.measure_eq_iSup_isCompact, hs.measure_eq_iSup_isCompact]

Result:
case h
G : Type u_1
inst✝¹⁰ : TopologicalSpace G
inst✝⁹ : Group G
inst✝⁸ : IsTopologicalGroup G
inst✝⁷ : MeasurableSpace G
inst✝⁶ : BorelSpace G
inst✝⁵ : LocallyCompactSpace G
μ' μ : Measure G
inst✝⁴ : μ.IsHaarMeasure
inst✝³ : IsFiniteMeasureOnCompacts μ'
inst✝² : μ'.IsMulLeftInvariant
inst✝¹ : μ.InnerRegular
inst✝ : μ'.InnerRegular
s : Set G
hs : MeasurableSet s
⊢ ⨆ K, ⨆ (_ : K ⊆ s), ⨆ (_ : IsCompact K), μ' K = ⨆ K, ⨆ (_ : K ⊆ s), ⨆ (_ : IsCompact K), (μ'.haarScalarFactor μ • μ) K

Proof state:
case h
G : Type u_1
inst✝¹⁰ : TopologicalSpace G
inst✝⁹ : Group G
inst✝⁸ : IsTopologicalGroup G
inst✝⁷ : MeasurableSpace G
inst✝⁶ : BorelSpace G
inst✝⁵ : LocallyCompactSpace G
μ' μ : Measure G
inst✝⁴ : μ.IsHaarMeasure
inst✝³ : IsFiniteMeasureOnCompacts μ'
inst✝² : μ'.IsMulLeftInvariant
inst✝¹ : μ.InnerRegular
inst✝ : μ'.InnerRegular
s : Set G
hs : MeasurableSet s
⊢ ⨆ K, ⨆ (_ : K ⊆ s), ⨆ (_ : IsCompact K), μ' K = ⨆ K, ⨆ (_ : K ⊆ s), ⨆ (_ : IsCompact K), (μ'.haarScalarFactor μ • μ) K

Tactic:
congr! 4 with K _Ks K_comp

Result:
case h.h.e'_4.h.f.f
G : Type u_1
inst✝¹⁰ : TopologicalSpace G
inst✝⁹ : Group G
inst✝⁸ : IsTopologicalGroup G
inst✝⁷ : MeasurableSpace G
inst✝⁶ : BorelSpace G
inst✝⁵ : LocallyCompactSpace G
μ' μ : Measure G
inst✝⁴ : μ.IsHaarMeasure
inst✝³ : IsFiniteMeasureOnCompacts μ'
inst✝² : μ'.IsMulLeftInvariant
inst✝¹ : μ.InnerRegular
inst✝ : μ'.InnerRegular
s : Set G
hs : MeasurableSet s
K : Set G
_Ks : K ⊆ s
K_comp : IsCompact K
⊢ μ' K = (μ'.haarScalarFactor μ • μ) K