Theorem: MeasureTheory.Measure.haarScalarFactor_eq_mul
File: Mathlib/MeasureTheory/Measure/Haar/Unique.lean

Proof steps:
state_before: G : Type u_1
inst✝⁸ : TopologicalSpace G
inst✝⁷ : Group G
inst✝⁶ : TopologicalGroup G
inst✝⁵ : MeasurableSpace G
inst✝⁴ : BorelSpace G
μ' μ ν : Measure G
inst✝³ : μ.IsHaarMeasure
inst✝² : ν.IsHaarMeasure
inst✝¹ : IsFiniteMeasureOnCompacts μ'
inst✝ : μ'.IsMulLeftInvariant
⊢ μ'.haarScalarFactor ν = μ'.haarScalarFactor μ * μ.haarScalarFactor ν
state_after: case pos
G : Type u_1
inst✝⁸ : TopologicalSpace G
inst✝⁷ : Group G
inst✝⁶ : TopologicalGroup G
inst✝⁵ : MeasurableSpace G
inst✝⁴ : BorelSpace G
μ' μ ν : Measure G
inst✝³ : μ.IsHaarMeasure
inst✝² : ν.IsHaarMeasure
inst✝¹ : IsFiniteMeasureOnCompacts μ'
inst✝ : μ'.IsMulLeftInvariant
hG : LocallyCompactSpace G
⊢ μ'.haarScalarFactor ν = μ'.haarScalarFactor μ * μ.haarScalarFactor ν

case neg
G : Type u_1
inst✝⁸ : TopologicalSpace G
inst✝⁷ : Group G
inst✝⁶ : TopologicalGroup G
inst✝⁵ : MeasurableSpace G
inst✝⁴ : BorelSpace G
μ' μ ν : Measure G
inst✝³ : μ.IsHaarMeasure
inst✝² : ν.IsHaarMeasure
inst✝¹ : IsFiniteMeasureOnCompacts μ'
inst✝ : μ'.IsMulLeftInvariant
hG : ¬LocallyCompactSpace G
⊢ μ'.haarScalarFactor ν = μ'.haarScalarFactor μ * μ.haarScalarFactor ν
tactic: by_cases hG : LocallyCompactSpace G
state_before: case pos
G : Type u_1
inst✝⁸ : TopologicalSpace G
inst✝⁷ : Group G
inst✝⁶ : TopologicalGroup G
inst✝⁵ : MeasurableSpace G
inst✝⁴ : BorelSpace G
μ' μ ν : Measure G
inst✝³ : μ.IsHaarMeasure
inst✝² : ν.IsHaarMeasure
inst✝¹ : IsFiniteMeasureOnCompacts μ'
inst✝ : μ'.IsMulLeftInvariant
hG : LocallyCompactSpace G
⊢ μ'.haarScalarFactor ν = μ'.haarScalarFactor μ * μ.haarScalarFactor ν

case neg
G : Type u_1
inst✝⁸ : TopologicalSpace G
inst✝⁷ : Group G
inst✝⁶ : TopologicalGroup G
inst✝⁵ : MeasurableSpace G
inst✝⁴ : BorelSpace G
μ' μ ν : Measure G
inst✝³ : μ.IsHaarMeasure
inst✝² : ν.IsHaarMeasure
inst✝¹ : IsFiniteMeasureOnCompacts μ'
inst✝ : μ'.IsMulLeftInvariant
hG : ¬LocallyCompactSpace G
⊢ μ'.haarScalarFactor ν = μ'.haarScalarFactor μ * μ.haarScalarFactor ν
state_after: case neg
G : Type u_1
inst✝⁸ : TopologicalSpace G
inst✝⁷ : Group G
inst✝⁶ : TopologicalGroup G
inst✝⁵ : MeasurableSpace G
inst✝⁴ : BorelSpace G
μ' μ ν : Measure G
inst✝³ : μ.IsHaarMeasure
inst✝² : ν.IsHaarMeasure
inst✝¹ : IsFiniteMeasureOnCompacts μ'
inst✝ : μ'.IsMulLeftInvariant
hG : ¬LocallyCompactSpace G
⊢ μ'.haarScalarFactor ν = μ'.haarScalarFactor μ * μ.haarScalarFactor ν

case pos
G : Type u_1
inst✝⁸ : TopologicalSpace G
inst✝⁷ : Group G
inst✝⁶ : TopologicalGroup G
inst✝⁵ : MeasurableSpace G
inst✝⁴ : BorelSpace G
μ' μ ν : Measure G
inst✝³ : μ.IsHaarMeasure
inst✝² : ν.IsHaarMeasure
inst✝¹ : IsFiniteMeasureOnCompacts μ'
inst✝ : μ'.IsMulLeftInvariant
hG : LocallyCompactSpace G
⊢ μ'.haarScalarFactor ν = μ'.haarScalarFactor μ * μ.haarScalarFactor ν
tactic: swap
state_before: case pos
G : Type u_1
inst✝⁸ : TopologicalSpace G
inst✝⁷ : Group G
inst✝⁶ : TopologicalGroup G
inst✝⁵ : MeasurableSpace G
inst✝⁴ : BorelSpace G
μ' μ ν : Measure G
inst✝³ : μ.IsHaarMeasure
inst✝² : ν.IsHaarMeasure
inst✝¹ : IsFiniteMeasureOnCompacts μ'
inst✝ : μ'.IsMulLeftInvariant
hG : LocallyCompactSpace G
⊢ μ'.haarScalarFactor ν = μ'.haarScalarFactor μ * μ.haarScalarFactor ν
state_after: case pos.intro.mk.intro.intro
G : Type u_1
inst✝⁸ : TopologicalSpace G
inst✝⁷ : Group G
inst✝⁶ : TopologicalGroup G
inst✝⁵ : MeasurableSpace G
inst✝⁴ : BorelSpace G
μ' μ ν : Measure G
inst✝³ : μ.IsHaarMeasure
inst✝² : ν.IsHaarMeasure
inst✝¹ : IsFiniteMeasureOnCompacts μ'
inst✝ : μ'.IsMulLeftInvariant
hG : LocallyCompactSpace G
g : G → ℝ
g_cont : Continuous g
g_comp : HasCompactSupport ⇑{ toFun := g, continuous_toFun := g_cont }
g_nonneg : 0 ≤ { toFun := g, continuous_toFun := g_cont }
g_one : { toFun := g, continuous_toFun := g_cont } 1 ≠ 0
⊢ μ'.haarScalarFactor ν = μ'.haarScalarFactor μ * μ.haarScalarFactor ν
tactic: obtain ⟨⟨g, g_cont⟩, g_comp, g_nonneg, g_one⟩ :
    ∃ (g : C(G, ℝ)), HasCompactSupport g ∧ 0 ≤ g ∧ g 1 ≠ 0 := exists_continuous_nonneg_pos 1
state_before: case pos.intro.mk.intro.intro
G : Type u_1
inst✝⁸ : TopologicalSpace G
inst✝⁷ : Group G
inst✝⁶ : TopologicalGroup G
inst✝⁵ : MeasurableSpace G
inst✝⁴ : BorelSpace G
μ' μ ν : Measure G
inst✝³ : μ.IsHaarMeasure
inst✝² : ν.IsHaarMeasure
inst✝¹ : IsFiniteMeasureOnCompacts μ'
inst✝ : μ'.IsMulLeftInvariant
hG : LocallyCompactSpace G
g : G → ℝ
g_cont : Continuous g
g_comp : HasCompactSupport ⇑{ toFun := g, continuous_toFun := g_cont }
g_nonneg : 0 ≤ { toFun := g, continuous_toFun := g_cont }
g_one : { toFun := g, continuous_toFun := g_cont } 1 ≠ 0
⊢ μ'.haarScalarFactor ν = μ'.haarScalarFactor μ * μ.haarScalarFactor ν
state_after: case pos.intro.mk.intro.intro
G : Type u_1
inst✝⁸ : TopologicalSpace G
inst✝⁷ : Group G
inst✝⁶ : TopologicalGroup G
inst✝⁵ : MeasurableSpace G
inst✝⁴ : BorelSpace G
μ' μ ν : Measure G
inst✝³ : μ.IsHaarMeasure
inst✝² : ν.IsHaarMeasure
inst✝¹ : IsFiniteMeasureOnCompacts μ'
inst✝ : μ'.IsMulLeftInvariant
hG : LocallyCompactSpace G
g : G → ℝ
g_cont : Continuous g
g_comp : HasCompactSupport ⇑{ toFun := g, continuous_toFun := g_cont }
g_nonneg : 0 ≤ { toFun := g, continuous_toFun := g_cont }
g_one : { toFun := g, continuous_toFun := g_cont } 1 ≠ 0
Z : ∫ (x : G), g x ∂μ' = ∫ (x : G), g x ∂μ'.haarScalarFactor μ • μ
⊢ μ'.haarScalarFactor ν = μ'.haarScalarFactor μ * μ.haarScalarFactor ν
tactic: have Z := integral_isMulLeftInvariant_eq_smul_of_hasCompactSupport μ' μ g_cont g_comp
state_before: case pos.intro.mk.intro.intro
G : Type u_1
inst✝⁸ : TopologicalSpace G
inst✝⁷ : Group G
inst✝⁶ : TopologicalGroup G
inst✝⁵ : MeasurableSpace G
inst✝⁴ : BorelSpace G
μ' μ ν : Measure G
inst✝³ : μ.IsHaarMeasure
inst✝² : ν.IsHaarMeasure
inst✝¹ : IsFiniteMeasureOnCompacts μ'
inst✝ : μ'.IsMulLeftInvariant
hG : LocallyCompactSpace G
g : G → ℝ
g_cont : Continuous g
g_comp : HasCompactSupport ⇑{ toFun := g, continuous_toFun := g_cont }
g_nonneg : 0 ≤ { toFun := g, continuous_toFun := g_cont }
g_one : { toFun := g, continuous_toFun := g_cont } 1 ≠ 0
Z : ∫ (x : G), g x ∂μ' = ∫ (x : G), g x ∂μ'.haarScalarFactor μ • μ
⊢ μ'.haarScalarFactor ν = μ'.haarScalarFactor μ * μ.haarScalarFactor ν
state_after: case pos.intro.mk.intro.intro
G : Type u_1
inst✝⁸ : TopologicalSpace G
inst✝⁷ : Group G
inst✝⁶ : TopologicalGroup G
inst✝⁵ : MeasurableSpace G
inst✝⁴ : BorelSpace G
μ' μ ν : Measure G
inst✝³ : μ.IsHaarMeasure
inst✝² : ν.IsHaarMeasure
inst✝¹ : IsFiniteMeasureOnCompacts μ'
inst✝ : μ'.IsMulLeftInvariant
hG : LocallyCompactSpace G
g : G → ℝ
g_cont : Continuous g
g_comp : HasCompactSupport ⇑{ toFun := g, continuous_toFun := g_cont }
g_nonneg : 0 ≤ { toFun := g, continuous_toFun := g_cont }
g_one : { toFun := g, continuous_toFun := g_cont } 1 ≠ 0
Z : μ'.haarScalarFactor ν • ∫ (x : G), g x ∂ν = (μ'.haarScalarFactor μ * μ.haarScalarFactor ν) • ∫ (x : G), g x ∂ν
⊢ μ'.haarScalarFactor ν = μ'.haarScalarFactor μ * μ.haarScalarFactor ν
tactic: simp only [integral_smul_nnreal_measure, smul_smul,
    integral_isMulLeftInvariant_eq_smul_of_hasCompactSupport μ' ν g_cont g_comp,
    integral_isMulLeftInvariant_eq_smul_of_hasCompactSupport μ ν g_cont g_comp] at Z
state_before: case pos.intro.mk.intro.intro
G : Type u_1
inst✝⁸ : TopologicalSpace G
inst✝⁷ : Group G
inst✝⁶ : TopologicalGroup G
inst✝⁵ : MeasurableSpace G
inst✝⁴ : BorelSpace G
μ' μ ν : Measure G
inst✝³ : μ.IsHaarMeasure
inst✝² : ν.IsHaarMeasure
inst✝¹ : IsFiniteMeasureOnCompacts μ'
inst✝ : μ'.IsMulLeftInvariant
hG : LocallyCompactSpace G
g : G → ℝ
g_cont : Continuous g
g_comp : HasCompactSupport ⇑{ toFun := g, continuous_toFun := g_cont }
g_nonneg : 0 ≤ { toFun := g, continuous_toFun := g_cont }
g_one : { toFun := g, continuous_toFun := g_cont } 1 ≠ 0
Z : μ'.haarScalarFactor ν • ∫ (x : G), g x ∂ν = (μ'.haarScalarFactor μ * μ.haarScalarFactor ν) • ∫ (x : G), g x ∂ν
int_g_pos : 0 < ∫ (x : G), g x ∂ν
⊢ μ'.haarScalarFactor ν = μ'.haarScalarFactor μ * μ.haarScalarFactor ν
state_after: case pos.intro.mk.intro.intro
G : Type u_1
inst✝⁸ : TopologicalSpace G
inst✝⁷ : Group G
inst✝⁶ : TopologicalGroup G
inst✝⁵ : MeasurableSpace G
inst✝⁴ : BorelSpace G
μ' μ ν : Measure G
inst✝³ : μ.IsHaarMeasure
inst✝² : ν.IsHaarMeasure
inst✝¹ : IsFiniteMeasureOnCompacts μ'
inst✝ : μ'.IsMulLeftInvariant
hG : LocallyCompactSpace G
g : G → ℝ
g_cont : Continuous g
g_comp : HasCompactSupport ⇑{ toFun := g, continuous_toFun := g_cont }
g_nonneg : 0 ≤ { toFun := g, continuous_toFun := g_cont }
g_one : { toFun := g, continuous_toFun := g_cont } 1 ≠ 0
int_g_pos : 0 < ∫ (x : G), g x ∂ν
Z : ↑(μ'.haarScalarFactor ν) * ∫ (x : G), g x ∂ν = ↑(μ'.haarScalarFactor μ * μ.haarScalarFactor ν) * ∫ (x : G), g x ∂ν
⊢ μ'.haarScalarFactor ν = μ'.haarScalarFactor μ * μ.haarScalarFactor ν
tactic: change (haarScalarFactor μ' ν : ℝ) * ∫ (x : G), g x ∂ν =
    (haarScalarFactor μ' μ * haarScalarFactor μ ν : ℝ≥0) * ∫ (x : G), g x ∂ν at Z
state_before: case pos.intro.mk.intro.intro
G : Type u_1
inst✝⁸ : TopologicalSpace G
inst✝⁷ : Group G
inst✝⁶ : TopologicalGroup G
inst✝⁵ : MeasurableSpace G
inst✝⁴ : BorelSpace G
μ' μ ν : Measure G
inst✝³ : μ.IsHaarMeasure
inst✝² : ν.IsHaarMeasure
inst✝¹ : IsFiniteMeasureOnCompacts μ'
inst✝ : μ'.IsMulLeftInvariant
hG : LocallyCompactSpace G
g : G → ℝ
g_cont : Continuous g
g_comp : HasCompactSupport ⇑{ toFun := g, continuous_toFun := g_cont }
g_nonneg : 0 ≤ { toFun := g, continuous_toFun := g_cont }
g_one : { toFun := g, continuous_toFun := g_cont } 1 ≠ 0
int_g_pos : 0 < ∫ (x : G), g x ∂ν
Z : ↑(μ'.haarScalarFactor ν) * ∫ (x : G), g x ∂ν = ↑(μ'.haarScalarFactor μ * μ.haarScalarFactor ν) * ∫ (x : G), g x ∂ν
⊢ μ'.haarScalarFactor ν = μ'.haarScalarFactor μ * μ.haarScalarFactor ν
state_after: no goals
tactic: simpa only [mul_eq_mul_right_iff (M₀ := ℝ), int_g_pos.ne', or_false, NNReal.eq_iff] using Z