-- Mathlib/MeasureTheory/Measure/Haar/Basic.lean
theorem is_left_invariant_chaar {K₀ : PositiveCompacts G} (g : G) (K : Compacts G) :
    chaar K₀ (K.map _ <| continuous_mul_left g) = chaar K₀ K

Proof state:
G : Type u_1
inst✝² : Group G
inst✝¹ : TopologicalSpace G
inst✝ : IsTopologicalGroup G
K₀ : PositiveCompacts G
g : G
K : Compacts G
eval : (Compacts G → ℝ) → ℝ := fun f => f (Compacts.map (fun b => g * b) ⋯ K) - f K
this : Continuous eval
⊢ closure (prehaar ↑K₀ '' {U | U ⊆ ↑⊤.toOpens ∧ IsOpen U ∧ 1 ∈ U}) ⊆ eval ⁻¹' {0}

Tactic:
rw [IsClosed.closure_subset_iff]

Result:
G : Type u_1
inst✝² : Group G
inst✝¹ : TopologicalSpace G
inst✝ : IsTopologicalGroup G
K₀ : PositiveCompacts G
g : G
K : Compacts G
eval : (Compacts G → ℝ) → ℝ := fun f => f (Compacts.map (fun b => g * b) ⋯ K) - f K
this : Continuous eval
⊢ prehaar ↑K₀ '' {U | U ⊆ ↑⊤.toOpens ∧ IsOpen U ∧ 1 ∈ U} ⊆ eval ⁻¹' {0}

G : Type u_1
inst✝² : Group G
inst✝¹ : TopologicalSpace G
inst✝ : IsTopologicalGroup G
K₀ : PositiveCompacts G
g : G
K : Compacts G
eval : (Compacts G → ℝ) → ℝ := fun f => f (Compacts.map (fun b => g * b) ⋯ K) - f K
this : Continuous eval
⊢ IsClosed (eval ⁻¹' {0})

Proof state:
case intro.intro.intro.intro
G : Type u_1
inst✝² : Group G
inst✝¹ : TopologicalSpace G
inst✝ : IsTopologicalGroup G
K₀ : PositiveCompacts G
g : G
K : Compacts G
eval : (Compacts G → ℝ) → ℝ := fun f => f (Compacts.map (fun b => g * b) ⋯ K) - f K
this : Continuous eval
U : Set G
left✝ : U ⊆ ↑⊤.toOpens
h2U : IsOpen U
h3U : 1 ∈ U
⊢ prehaar (↑K₀) U ∈ eval ⁻¹' {0}

Tactic:
simp only [eval, mem_singleton_iff, mem_preimage, sub_eq_zero]

Result:
case intro.intro.intro.intro
G : Type u_1
inst✝² : Group G
inst✝¹ : TopologicalSpace G
inst✝ : IsTopologicalGroup G
K₀ : PositiveCompacts G
g : G
K : Compacts G
eval : (Compacts G → ℝ) → ℝ := fun f => f (Compacts.map (fun b => g * b) ⋯ K) - f K
this : Continuous eval
U : Set G
left✝ : U ⊆ ↑⊤.toOpens
h2U : IsOpen U
h3U : 1 ∈ U
⊢ prehaar (↑K₀) U (Compacts.map (fun b => g * b) ⋯ K) = prehaar (↑K₀) U K

Proof state:
G : Type u_1
inst✝² : Group G
inst✝¹ : TopologicalSpace G
inst✝ : IsTopologicalGroup G
K₀ : PositiveCompacts G
g : G
K : Compacts G
⊢ chaar K₀ (Compacts.map (fun b => g * b) ⋯ K) = chaar K₀ K

Tactic:
let eval : (Compacts G → ℝ) → ℝ := fun f => f (K.map _ <| continuous_mul_left g) - f K

Result:
G : Type u_1
inst✝² : Group G
inst✝¹ : TopologicalSpace G
inst✝ : IsTopologicalGroup G
K₀ : PositiveCompacts G
g : G
K : Compacts G
eval : (Compacts G → ℝ) → ℝ := fun f => f (Compacts.map (fun b => g * b) ⋯ K) - f K
⊢ chaar K₀ (Compacts.map (fun b => g * b) ⋯ K) = chaar K₀ K

Proof state:
case intro.intro.intro.intro
G : Type u_1
inst✝² : Group G
inst✝¹ : TopologicalSpace G
inst✝ : IsTopologicalGroup G
K₀ : PositiveCompacts G
g : G
K : Compacts G
eval : (Compacts G → ℝ) → ℝ := fun f => f (Compacts.map (fun b => g * b) ⋯ K) - f K
this : Continuous eval
U : Set G
left✝ : U ⊆ ↑⊤.toOpens
h2U : IsOpen U
h3U : 1 ∈ U
⊢ prehaar (↑K₀) U (Compacts.map (fun b => g * b) ⋯ K) = prehaar (↑K₀) U K

Tactic:
apply is_left_invariant_prehaar

Result:
case intro.intro.intro.intro.hU
G : Type u_1
inst✝² : Group G
inst✝¹ : TopologicalSpace G
inst✝ : IsTopologicalGroup G
K₀ : PositiveCompacts G
g : G
K : Compacts G
eval : (Compacts G → ℝ) → ℝ := fun f => f (Compacts.map (fun b => g * b) ⋯ K) - f K
this : Continuous eval
U : Set G
left✝ : U ⊆ ↑⊤.toOpens
h2U : IsOpen U
h3U : 1 ∈ U
⊢ (interior U).Nonempty

Proof state:
G : Type u_1
inst✝² : Group G
inst✝¹ : TopologicalSpace G
inst✝ : IsTopologicalGroup G
K₀ : PositiveCompacts G
g : G
K : Compacts G
eval : (Compacts G → ℝ) → ℝ := fun f => f (Compacts.map (fun b => g * b) ⋯ K) - f K
this : Continuous eval
⊢ prehaar ↑K₀ '' {U | U ⊆ ↑⊤.toOpens ∧ IsOpen U ∧ 1 ∈ U} ⊆ eval ⁻¹' {0}

Tactic:
rintro _ ⟨U, ⟨_, h2U, h3U⟩, rfl⟩

Result:
case intro.intro.intro.intro
G : Type u_1
inst✝² : Group G
inst✝¹ : TopologicalSpace G
inst✝ : IsTopologicalGroup G
K₀ : PositiveCompacts G
g : G
K : Compacts G
eval : (Compacts G → ℝ) → ℝ := fun f => f (Compacts.map (fun b => g * b) ⋯ K) - f K
this : Continuous eval
U : Set G
left✝ : U ⊆ ↑⊤.toOpens
h2U : IsOpen U
h3U : 1 ∈ U
⊢ prehaar (↑K₀) U ∈ eval ⁻¹' {0}

Proof state:
G : Type u_1
inst✝² : Group G
inst✝¹ : TopologicalSpace G
inst✝ : IsTopologicalGroup G
K₀ : PositiveCompacts G
g : G
K : Compacts G
eval : (Compacts G → ℝ) → ℝ := fun f => f (Compacts.map (fun b => g * b) ⋯ K) - f K
this : Continuous eval
⊢ IsClosed (eval ⁻¹' {0})

Tactic:
apply continuous_iff_isClosed.mp this

Result:
case a
G : Type u_1
inst✝² : Group G
inst✝¹ : TopologicalSpace G
inst✝ : IsTopologicalGroup G
K₀ : PositiveCompacts G
g : G
K : Compacts G
eval : (Compacts G → ℝ) → ℝ := fun f => f (Compacts.map (fun b => g * b) ⋯ K) - f K
this : Continuous eval
⊢ IsClosed {0}

Proof state:
G : Type u_1
inst✝² : Group G
inst✝¹ : TopologicalSpace G
inst✝ : IsTopologicalGroup G
K₀ : PositiveCompacts G
g : G
K : Compacts G
eval : (Compacts G → ℝ) → ℝ := fun f => f (Compacts.map (fun b => g * b) ⋯ K) - f K
⊢ chaar K₀ (Compacts.map (fun b => g * b) ⋯ K) = chaar K₀ K

Tactic:
have : Continuous eval := (continuous_apply (K.map _ _)).sub (continuous_apply K)

Result:
G : Type u_1
inst✝² : Group G
inst✝¹ : TopologicalSpace G
inst✝ : IsTopologicalGroup G
K₀ : PositiveCompacts G
g : G
K : Compacts G
eval : (Compacts G → ℝ) → ℝ := fun f => f (Compacts.map (fun b => g * b) ⋯ K) - f K
this : Continuous eval
⊢ chaar K₀ (Compacts.map (fun b => g * b) ⋯ K) = chaar K₀ K

Proof state:
G : Type u_1
inst✝² : Group G
inst✝¹ : TopologicalSpace G
inst✝ : IsTopologicalGroup G
K₀ : PositiveCompacts G
g : G
K : Compacts G
eval : (Compacts G → ℝ) → ℝ := fun f => f (Compacts.map (fun b => g * b) ⋯ K) - f K
this : Continuous eval
⊢ chaar K₀ (Compacts.map (fun b => g * b) ⋯ K) = chaar K₀ K

Tactic:
rw [← sub_eq_zero]

Result:
G : Type u_1
inst✝² : Group G
inst✝¹ : TopologicalSpace G
inst✝ : IsTopologicalGroup G
K₀ : PositiveCompacts G
g : G
K : Compacts G
eval : (Compacts G → ℝ) → ℝ := fun f => f (Compacts.map (fun b => g * b) ⋯ K) - f K
this : Continuous eval
⊢ chaar K₀ (Compacts.map (fun b => g * b) ⋯ K) - chaar K₀ K = 0

Proof state:
case intro.intro.intro.intro.hU
G : Type u_1
inst✝² : Group G
inst✝¹ : TopologicalSpace G
inst✝ : IsTopologicalGroup G
K₀ : PositiveCompacts G
g : G
K : Compacts G
eval : (Compacts G → ℝ) → ℝ := fun f => f (Compacts.map (fun b => g * b) ⋯ K) - f K
this : Continuous eval
U : Set G
left✝ : U ⊆ ↑⊤.toOpens
h2U : IsOpen U
h3U : 1 ∈ U
⊢ U.Nonempty

Tactic:
exact ⟨1, h3U⟩

Result:
no goals

Proof state:
case a
G : Type u_1
inst✝² : Group G
inst✝¹ : TopologicalSpace G
inst✝ : IsTopologicalGroup G
K₀ : PositiveCompacts G
g : G
K : Compacts G
eval : (Compacts G → ℝ) → ℝ := fun f => f (Compacts.map (fun b => g * b) ⋯ K) - f K
this : Continuous eval
⊢ IsClosed {0}

Tactic:
exact isClosed_singleton

Result:
no goals

Proof state:
case intro.intro.intro.intro.hU
G : Type u_1
inst✝² : Group G
inst✝¹ : TopologicalSpace G
inst✝ : IsTopologicalGroup G
K₀ : PositiveCompacts G
g : G
K : Compacts G
eval : (Compacts G → ℝ) → ℝ := fun f => f (Compacts.map (fun b => g * b) ⋯ K) - f K
this : Continuous eval
U : Set G
left✝ : U ⊆ ↑⊤.toOpens
h2U : IsOpen U
h3U : 1 ∈ U
⊢ (interior U).Nonempty

Tactic:
rw [h2U.interior_eq]

Result:
case intro.intro.intro.intro.hU
G : Type u_1
inst✝² : Group G
inst✝¹ : TopologicalSpace G
inst✝ : IsTopologicalGroup G
K₀ : PositiveCompacts G
g : G
K : Compacts G
eval : (Compacts G → ℝ) → ℝ := fun f => f (Compacts.map (fun b => g * b) ⋯ K) - f K
this : Continuous eval
U : Set G
left✝ : U ⊆ ↑⊤.toOpens
h2U : IsOpen U
h3U : 1 ∈ U
⊢ U.Nonempty