-- Mathlib/Analysis/Convex/Exposed.lean
theorem sInter [ContinuousAdd 𝕜] {F : Finset (Set E)} (hF : F.Nonempty)
    (hAF : ∀ B ∈ F, IsExposed 𝕜 A B) : IsExposed 𝕜 A (⋂₀ F)

Proof state:
case insert.inr
𝕜 : Type u_1
E : Type u_2
inst✝⁵ : TopologicalSpace 𝕜
inst✝⁴ : OrderedRing 𝕜
inst✝³ : AddCommMonoid E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
A : Set E
inst✝ : ContinuousAdd 𝕜
C : Set E
F : Finset (Set E)
a✝ : C ∉ F
hF' : F.Nonempty → (∀ B ∈ F, IsExposed 𝕜 A B) → IsExposed 𝕜 A (⋂₀ ↑F)
hF : (insert C F).Nonempty
hAF : ∀ B ∈ insert C F, IsExposed 𝕜 A B
hFnemp : F.Nonempty
⊢ IsExposed 𝕜 A (C ∩ ⋂₀ ↑F)

Tactic:
exact (hAF C (Finset.mem_insert_self C F)).inter
  (hF' hFnemp fun B hB => hAF B (Finset.mem_insert_of_mem hB))

Result:
no goals

Proof state:
case empty
𝕜 : Type u_1
E : Type u_2
inst✝⁵ : TopologicalSpace 𝕜
inst✝⁴ : OrderedRing 𝕜
inst✝³ : AddCommMonoid E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
A : Set E
inst✝ : ContinuousAdd 𝕜
hF : ∅.Nonempty
hAF : ∀ B ∈ ∅, IsExposed 𝕜 A B
⊢ False

Tactic:
exact Finset.not_nonempty_empty hF

Result:
no goals

Proof state:
case empty
𝕜 : Type u_1
E : Type u_2
inst✝⁵ : TopologicalSpace 𝕜
inst✝⁴ : OrderedRing 𝕜
inst✝³ : AddCommMonoid E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
A : Set E
inst✝ : ContinuousAdd 𝕜
hF : ∅.Nonempty
hAF : ∀ B ∈ ∅, IsExposed 𝕜 A B
⊢ IsExposed 𝕜 A (⋂₀ ↑∅)

Tactic:
exfalso

Result:
case empty
𝕜 : Type u_1
E : Type u_2
inst✝⁵ : TopologicalSpace 𝕜
inst✝⁴ : OrderedRing 𝕜
inst✝³ : AddCommMonoid E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
A : Set E
inst✝ : ContinuousAdd 𝕜
hF : ∅.Nonempty
hAF : ∀ B ∈ ∅, IsExposed 𝕜 A B
⊢ False

Proof state:
case insert
𝕜 : Type u_1
E : Type u_2
inst✝⁵ : TopologicalSpace 𝕜
inst✝⁴ : OrderedRing 𝕜
inst✝³ : AddCommMonoid E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
A : Set E
inst✝ : ContinuousAdd 𝕜
C : Set E
F : Finset (Set E)
a✝ : C ∉ F
hF' : F.Nonempty → (∀ B ∈ F, IsExposed 𝕜 A B) → IsExposed 𝕜 A (⋂₀ ↑F)
hF : (insert C F).Nonempty
hAF : ∀ B ∈ insert C F, IsExposed 𝕜 A B
⊢ IsExposed 𝕜 A (C ∩ ⋂₀ ↑F)

Tactic:
obtain rfl | hFnemp := F.eq_empty_or_nonempty

Result:
case insert.inl
𝕜 : Type u_1
E : Type u_2
inst✝⁵ : TopologicalSpace 𝕜
inst✝⁴ : OrderedRing 𝕜
inst✝³ : AddCommMonoid E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
A : Set E
inst✝ : ContinuousAdd 𝕜
C : Set E
a✝ : C ∉ ∅
hF' : ∅.Nonempty → (∀ B ∈ ∅, IsExposed 𝕜 A B) → IsExposed 𝕜 A (⋂₀ ↑∅)
hF : (insert C ∅).Nonempty
hAF : ∀ B ∈ insert C ∅, IsExposed 𝕜 A B
⊢ IsExposed 𝕜 A (C ∩ ⋂₀ ↑∅)

case insert.inr
𝕜 : Type u_1
E : Type u_2
inst✝⁵ : TopologicalSpace 𝕜
inst✝⁴ : OrderedRing 𝕜
inst✝³ : AddCommMonoid E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
A : Set E
inst✝ : ContinuousAdd 𝕜
C : Set E
F : Finset (Set E)
a✝ : C ∉ F
hF' : F.Nonempty → (∀ B ∈ F, IsExposed 𝕜 A B) → IsExposed 𝕜 A (⋂₀ ↑F)
hF : (insert C F).Nonempty
hAF : ∀ B ∈ insert C F, IsExposed 𝕜 A B
hFnemp : F.Nonempty
⊢ IsExposed 𝕜 A (C ∩ ⋂₀ ↑F)

Proof state:
case insert.inl
𝕜 : Type u_1
E : Type u_2
inst✝⁵ : TopologicalSpace 𝕜
inst✝⁴ : OrderedRing 𝕜
inst✝³ : AddCommMonoid E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
A : Set E
inst✝ : ContinuousAdd 𝕜
C : Set E
a✝ : C ∉ ∅
hF' : ∅.Nonempty → (∀ B ∈ ∅, IsExposed 𝕜 A B) → IsExposed 𝕜 A (⋂₀ ↑∅)
hF : (insert C ∅).Nonempty
hAF : ∀ B ∈ insert C ∅, IsExposed 𝕜 A B
⊢ IsExposed 𝕜 A (C ∩ ⋂₀ ↑∅)

Tactic:
rw [Finset.coe_empty, sInter_empty, inter_univ]

Result:
case insert.inl
𝕜 : Type u_1
E : Type u_2
inst✝⁵ : TopologicalSpace 𝕜
inst✝⁴ : OrderedRing 𝕜
inst✝³ : AddCommMonoid E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
A : Set E
inst✝ : ContinuousAdd 𝕜
C : Set E
a✝ : C ∉ ∅
hF' : ∅.Nonempty → (∀ B ∈ ∅, IsExposed 𝕜 A B) → IsExposed 𝕜 A (⋂₀ ↑∅)
hF : (insert C ∅).Nonempty
hAF : ∀ B ∈ insert C ∅, IsExposed 𝕜 A B
⊢ IsExposed 𝕜 A C

Proof state:
case insert.inl
𝕜 : Type u_1
E : Type u_2
inst✝⁵ : TopologicalSpace 𝕜
inst✝⁴ : OrderedRing 𝕜
inst✝³ : AddCommMonoid E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
A : Set E
inst✝ : ContinuousAdd 𝕜
C : Set E
a✝ : C ∉ ∅
hF' : ∅.Nonempty → (∀ B ∈ ∅, IsExposed 𝕜 A B) → IsExposed 𝕜 A (⋂₀ ↑∅)
hF : (insert C ∅).Nonempty
hAF : ∀ B ∈ insert C ∅, IsExposed 𝕜 A B
⊢ IsExposed 𝕜 A C

Tactic:
exact hAF C (Finset.mem_singleton_self C)

Result:
no goals

Proof state:
case insert
𝕜 : Type u_1
E : Type u_2
inst✝⁵ : TopologicalSpace 𝕜
inst✝⁴ : OrderedRing 𝕜
inst✝³ : AddCommMonoid E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
A : Set E
inst✝ : ContinuousAdd 𝕜
C : Set E
F : Finset (Set E)
a✝ : C ∉ F
hF' : F.Nonempty → (∀ B ∈ F, IsExposed 𝕜 A B) → IsExposed 𝕜 A (⋂₀ ↑F)
hF : (insert C F).Nonempty
hAF : ∀ B ∈ insert C F, IsExposed 𝕜 A B
⊢ IsExposed 𝕜 A (⋂₀ ↑(insert C F))

Tactic:
rw [Finset.coe_insert, sInter_insert]

Result:
case insert
𝕜 : Type u_1
E : Type u_2
inst✝⁵ : TopologicalSpace 𝕜
inst✝⁴ : OrderedRing 𝕜
inst✝³ : AddCommMonoid E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
A : Set E
inst✝ : ContinuousAdd 𝕜
C : Set E
F : Finset (Set E)
a✝ : C ∉ F
hF' : F.Nonempty → (∀ B ∈ F, IsExposed 𝕜 A B) → IsExposed 𝕜 A (⋂₀ ↑F)
hF : (insert C F).Nonempty
hAF : ∀ B ∈ insert C F, IsExposed 𝕜 A B
⊢ IsExposed 𝕜 A (C ∩ ⋂₀ ↑F)