Theorem: surjOn_extremePoints_image
File: Mathlib/Analysis/Convex/KreinMilman.lean

Proof steps:
state_before: E : Type u_1
F : Type u_2
inst✝¹⁰ : AddCommGroup E
inst✝⁹ : Module ℝ E
inst✝⁸ : TopologicalSpace E
inst✝⁷ : T2Space E
inst✝⁶ : TopologicalAddGroup E
inst✝⁵ : ContinuousSMul ℝ E
inst✝⁴ : LocallyConvexSpace ℝ E
s : Set E
inst✝³ : AddCommGroup F
inst✝² : Module ℝ F
inst✝¹ : TopologicalSpace F
inst✝ : T1Space F
f : E →ᴬ[ℝ] F
hs : IsCompact s
⊢ SurjOn (⇑f) (extremePoints ℝ s) (extremePoints ℝ (⇑f '' s))
state_after: E : Type u_1
F : Type u_2
inst✝¹⁰ : AddCommGroup E
inst✝⁹ : Module ℝ E
inst✝⁸ : TopologicalSpace E
inst✝⁷ : T2Space E
inst✝⁶ : TopologicalAddGroup E
inst✝⁵ : ContinuousSMul ℝ E
inst✝⁴ : LocallyConvexSpace ℝ E
s : Set E
inst✝³ : AddCommGroup F
inst✝² : Module ℝ F
inst✝¹ : TopologicalSpace F
inst✝ : T1Space F
f : E →ᴬ[ℝ] F
hs : IsCompact s
w : F
hw : w ∈ extremePoints ℝ (⇑f '' s)
⊢ w ∈ ⇑f '' extremePoints ℝ s
tactic: rintro w hw
state_before: E : Type u_1
F : Type u_2
inst✝¹⁰ : AddCommGroup E
inst✝⁹ : Module ℝ E
inst✝⁸ : TopologicalSpace E
inst✝⁷ : T2Space E
inst✝⁶ : TopologicalAddGroup E
inst✝⁵ : ContinuousSMul ℝ E
inst✝⁴ : LocallyConvexSpace ℝ E
s : Set E
inst✝³ : AddCommGroup F
inst✝² : Module ℝ F
inst✝¹ : TopologicalSpace F
inst✝ : T1Space F
f : E →ᴬ[ℝ] F
hs : IsCompact s
w : F
hw : w ∈ extremePoints ℝ (⇑f '' s)
⊢ w ∈ ⇑f '' extremePoints ℝ s
state_after: E : Type u_1
F : Type u_2
inst✝¹⁰ : AddCommGroup E
inst✝⁹ : Module ℝ E
inst✝⁸ : TopologicalSpace E
inst✝⁷ : T2Space E
inst✝⁶ : TopologicalAddGroup E
inst✝⁵ : ContinuousSMul ℝ E
inst✝⁴ : LocallyConvexSpace ℝ E
s : Set E
inst✝³ : AddCommGroup F
inst✝² : Module ℝ F
inst✝¹ : TopologicalSpace F
inst✝ : T1Space F
f : E →ᴬ[ℝ] F
hs : IsCompact s
w : F
hw : w ∈ extremePoints ℝ (⇑f '' s)
ht : IsCompact {x | x ∈ s ∧ f x = w}
⊢ w ∈ ⇑f '' extremePoints ℝ s
tactic: have ht : IsCompact {x ∈ s | f x = w} :=
    hs.inter_right <| isClosed_singleton.preimage f.continuous
state_before: E : Type u_1
F : Type u_2
inst✝¹⁰ : AddCommGroup E
inst✝⁹ : Module ℝ E
inst✝⁸ : TopologicalSpace E
inst✝⁷ : T2Space E
inst✝⁶ : TopologicalAddGroup E
inst✝⁵ : ContinuousSMul ℝ E
inst✝⁴ : LocallyConvexSpace ℝ E
s : Set E
inst✝³ : AddCommGroup F
inst✝² : Module ℝ F
inst✝¹ : TopologicalSpace F
inst✝ : T1Space F
f : E →ᴬ[ℝ] F
hs : IsCompact s
w : F
hw : w ∈ extremePoints ℝ (⇑f '' s)
ht : IsCompact {x | x ∈ s ∧ f x = w}
⊢ w ∈ ⇑f '' extremePoints ℝ s
state_after: E : Type u_1
F : Type u_2
inst✝¹⁰ : AddCommGroup E
inst✝⁹ : Module ℝ E
inst✝⁸ : TopologicalSpace E
inst✝⁷ : T2Space E
inst✝⁶ : TopologicalAddGroup E
inst✝⁵ : ContinuousSMul ℝ E
inst✝⁴ : LocallyConvexSpace ℝ E
s : Set E
inst✝³ : AddCommGroup F
inst✝² : Module ℝ F
inst✝¹ : TopologicalSpace F
inst✝ : T1Space F
f : E →ᴬ[ℝ] F
hs : IsCompact s
w : F
hw : w ∈ extremePoints ℝ (⇑f '' s)
ht : IsCompact {x | x ∈ s ∧ f x = w}
ht₀ : {x | x ∈ s ∧ f x = w}.Nonempty
⊢ w ∈ ⇑f '' extremePoints ℝ s
tactic: have ht₀ : {x ∈ s | f x = w}.Nonempty := by simpa using extremePoints_subset hw
state_before: E : Type u_1
F : Type u_2
inst✝¹⁰ : AddCommGroup E
inst✝⁹ : Module ℝ E
inst✝⁸ : TopologicalSpace E
inst✝⁷ : T2Space E
inst✝⁶ : TopologicalAddGroup E
inst✝⁵ : ContinuousSMul ℝ E
inst✝⁴ : LocallyConvexSpace ℝ E
s : Set E
inst✝³ : AddCommGroup F
inst✝² : Module ℝ F
inst✝¹ : TopologicalSpace F
inst✝ : T1Space F
f : E →ᴬ[ℝ] F
hs : IsCompact s
w : F
hw : w ∈ extremePoints ℝ (⇑f '' s)
ht : IsCompact {x | x ∈ s ∧ f x = w}
ht₀ : {x | x ∈ s ∧ f x = w}.Nonempty
⊢ w ∈ ⇑f '' extremePoints ℝ s
state_after: case intro.intro.intro
E : Type u_1
F : Type u_2
inst✝¹⁰ : AddCommGroup E
inst✝⁹ : Module ℝ E
inst✝⁸ : TopologicalSpace E
inst✝⁷ : T2Space E
inst✝⁶ : TopologicalAddGroup E
inst✝⁵ : ContinuousSMul ℝ E
inst✝⁴ : LocallyConvexSpace ℝ E
s : Set E
inst✝³ : AddCommGroup F
inst✝² : Module ℝ F
inst✝¹ : TopologicalSpace F
inst✝ : T1Space F
f : E →ᴬ[ℝ] F
hs : IsCompact s
x : E
hx : x ∈ s
hw : f x ∈ extremePoints ℝ (⇑f '' s)
ht : IsCompact {x_1 | x_1 ∈ s ∧ f x_1 = f x}
ht₀ : {x_1 | x_1 ∈ s ∧ f x_1 = f x}.Nonempty
hyt :
  ∀ ⦃x₁ : E⦄,
    x₁ ∈ {x_1 | x_1 ∈ s ∧ f x_1 = f x} →
      ∀ ⦃x₂ : E⦄, x₂ ∈ {x_1 | x_1 ∈ s ∧ f x_1 = f x} → x ∈ openSegment ℝ x₁ x₂ → x₁ = x ∧ x₂ = x
⊢ f x ∈ ⇑f '' extremePoints ℝ s
tactic: obtain ⟨x, ⟨hx, rfl⟩, hyt⟩ := ht.extremePoints_nonempty ht₀
state_before: case intro.intro.intro
E : Type u_1
F : Type u_2
inst✝¹⁰ : AddCommGroup E
inst✝⁹ : Module ℝ E
inst✝⁸ : TopologicalSpace E
inst✝⁷ : T2Space E
inst✝⁶ : TopologicalAddGroup E
inst✝⁵ : ContinuousSMul ℝ E
inst✝⁴ : LocallyConvexSpace ℝ E
s : Set E
inst✝³ : AddCommGroup F
inst✝² : Module ℝ F
inst✝¹ : TopologicalSpace F
inst✝ : T1Space F
f : E →ᴬ[ℝ] F
hs : IsCompact s
x : E
hx : x ∈ s
hw : f x ∈ extremePoints ℝ (⇑f '' s)
ht : IsCompact {x_1 | x_1 ∈ s ∧ f x_1 = f x}
ht₀ : {x_1 | x_1 ∈ s ∧ f x_1 = f x}.Nonempty
hyt :
  ∀ ⦃x₁ : E⦄,
    x₁ ∈ {x_1 | x_1 ∈ s ∧ f x_1 = f x} →
      ∀ ⦃x₂ : E⦄, x₂ ∈ {x_1 | x_1 ∈ s ∧ f x_1 = f x} → x ∈ openSegment ℝ x₁ x₂ → x₁ = x ∧ x₂ = x
⊢ f x ∈ ⇑f '' extremePoints ℝ s
state_after: case intro.intro.intro
E : Type u_1
F : Type u_2
inst✝¹⁰ : AddCommGroup E
inst✝⁹ : Module ℝ E
inst✝⁸ : TopologicalSpace E
inst✝⁷ : T2Space E
inst✝⁶ : TopologicalAddGroup E
inst✝⁵ : ContinuousSMul ℝ E
inst✝⁴ : LocallyConvexSpace ℝ E
s : Set E
inst✝³ : AddCommGroup F
inst✝² : Module ℝ F
inst✝¹ : TopologicalSpace F
inst✝ : T1Space F
f : E →ᴬ[ℝ] F
hs : IsCompact s
x : E
hx : x ∈ s
hw : f x ∈ extremePoints ℝ (⇑f '' s)
ht : IsCompact {x_1 | x_1 ∈ s ∧ f x_1 = f x}
ht₀ : {x_1 | x_1 ∈ s ∧ f x_1 = f x}.Nonempty
hyt :
  ∀ ⦃x₁ : E⦄,
    x₁ ∈ {x_1 | x_1 ∈ s ∧ f x_1 = f x} →
      ∀ ⦃x₂ : E⦄, x₂ ∈ {x_1 | x_1 ∈ s ∧ f x_1 = f x} → x ∈ openSegment ℝ x₁ x₂ → x₁ = x ∧ x₂ = x
y : E
hy : y ∈ s
z : E
hz : z ∈ s
hxyz : x ∈ openSegment ℝ y z
⊢ y = x ∧ z = x
tactic: refine mem_image_of_mem _ ⟨hx, fun y hy z hz hxyz ↦ ?_⟩
state_before: case intro.intro.intro
E : Type u_1
F : Type u_2
inst✝¹⁰ : AddCommGroup E
inst✝⁹ : Module ℝ E
inst✝⁸ : TopologicalSpace E
inst✝⁷ : T2Space E
inst✝⁶ : TopologicalAddGroup E
inst✝⁵ : ContinuousSMul ℝ E
inst✝⁴ : LocallyConvexSpace ℝ E
s : Set E
inst✝³ : AddCommGroup F
inst✝² : Module ℝ F
inst✝¹ : TopologicalSpace F
inst✝ : T1Space F
f : E →ᴬ[ℝ] F
hs : IsCompact s
x : E
hx : x ∈ s
hw : f x ∈ extremePoints ℝ (⇑f '' s)
ht : IsCompact {x_1 | x_1 ∈ s ∧ f x_1 = f x}
ht₀ : {x_1 | x_1 ∈ s ∧ f x_1 = f x}.Nonempty
hyt :
  ∀ ⦃x₁ : E⦄,
    x₁ ∈ {x_1 | x_1 ∈ s ∧ f x_1 = f x} →
      ∀ ⦃x₂ : E⦄, x₂ ∈ {x_1 | x_1 ∈ s ∧ f x_1 = f x} → x ∈ openSegment ℝ x₁ x₂ → x₁ = x ∧ x₂ = x
y : E
hy : y ∈ s
z : E
hz : z ∈ s
hxyz : x ∈ openSegment ℝ y z
⊢ y = x ∧ z = x
state_after: case intro.intro.intro
E : Type u_1
F : Type u_2
inst✝¹⁰ : AddCommGroup E
inst✝⁹ : Module ℝ E
inst✝⁸ : TopologicalSpace E
inst✝⁷ : T2Space E
inst✝⁶ : TopologicalAddGroup E
inst✝⁵ : ContinuousSMul ℝ E
inst✝⁴ : LocallyConvexSpace ℝ E
s : Set E
inst✝³ : AddCommGroup F
inst✝² : Module ℝ F
inst✝¹ : TopologicalSpace F
inst✝ : T1Space F
f : E →ᴬ[ℝ] F
hs : IsCompact s
x : E
hx : x ∈ s
hw : f x ∈ extremePoints ℝ (⇑f '' s)
ht : IsCompact {x_1 | x_1 ∈ s ∧ f x_1 = f x}
ht₀ : {x_1 | x_1 ∈ s ∧ f x_1 = f x}.Nonempty
hyt :
  ∀ ⦃x₁ : E⦄,
    x₁ ∈ {x_1 | x_1 ∈ s ∧ f x_1 = f x} →
      ∀ ⦃x₂ : E⦄, x₂ ∈ {x_1 | x_1 ∈ s ∧ f x_1 = f x} → x ∈ openSegment ℝ x₁ x₂ → x₁ = x ∧ x₂ = x
y : E
hy : y ∈ s
z : E
hz : z ∈ s
hxyz : x ∈ openSegment ℝ y z
this : (fun a => f a) '' openSegment ℝ y z = openSegment ℝ (f y) (f z)
⊢ y = x ∧ z = x
tactic: have := by simpa using image_openSegment _ f.toAffineMap y z
state_before: case intro.intro.intro
E : Type u_1
F : Type u_2
inst✝¹⁰ : AddCommGroup E
inst✝⁹ : Module ℝ E
inst✝⁸ : TopologicalSpace E
inst✝⁷ : T2Space E
inst✝⁶ : TopologicalAddGroup E
inst✝⁵ : ContinuousSMul ℝ E
inst✝⁴ : LocallyConvexSpace ℝ E
s : Set E
inst✝³ : AddCommGroup F
inst✝² : Module ℝ F
inst✝¹ : TopologicalSpace F
inst✝ : T1Space F
f : E →ᴬ[ℝ] F
hs : IsCompact s
x : E
hx : x ∈ s
hw : f x ∈ extremePoints ℝ (⇑f '' s)
ht : IsCompact {x_1 | x_1 ∈ s ∧ f x_1 = f x}
ht₀ : {x_1 | x_1 ∈ s ∧ f x_1 = f x}.Nonempty
hyt :
  ∀ ⦃x₁ : E⦄,
    x₁ ∈ {x_1 | x_1 ∈ s ∧ f x_1 = f x} →
      ∀ ⦃x₂ : E⦄, x₂ ∈ {x_1 | x_1 ∈ s ∧ f x_1 = f x} → x ∈ openSegment ℝ x₁ x₂ → x₁ = x ∧ x₂ = x
y : E
hy : y ∈ s
z : E
hz : z ∈ s
hxyz : x ∈ openSegment ℝ y z
this : (fun a => f a) '' openSegment ℝ y z = openSegment ℝ (f y) (f z)
⊢ y = x ∧ z = x
state_after: case intro.intro.intro
E : Type u_1
F : Type u_2
inst✝¹⁰ : AddCommGroup E
inst✝⁹ : Module ℝ E
inst✝⁸ : TopologicalSpace E
inst✝⁷ : T2Space E
inst✝⁶ : TopologicalAddGroup E
inst✝⁵ : ContinuousSMul ℝ E
inst✝⁴ : LocallyConvexSpace ℝ E
s : Set E
inst✝³ : AddCommGroup F
inst✝² : Module ℝ F
inst✝¹ : TopologicalSpace F
inst✝ : T1Space F
f : E →ᴬ[ℝ] F
hs : IsCompact s
x : E
hx : x ∈ s
hw : f x ∈ extremePoints ℝ (⇑f '' s)
ht : IsCompact {x_1 | x_1 ∈ s ∧ f x_1 = f x}
ht₀ : {x_1 | x_1 ∈ s ∧ f x_1 = f x}.Nonempty
hyt :
  ∀ ⦃x₁ : E⦄,
    x₁ ∈ {x_1 | x_1 ∈ s ∧ f x_1 = f x} →
      ∀ ⦃x₂ : E⦄, x₂ ∈ {x_1 | x_1 ∈ s ∧ f x_1 = f x} → x ∈ openSegment ℝ x₁ x₂ → x₁ = x ∧ x₂ = x
y : E
hy : y ∈ s
z : E
hz : z ∈ s
hxyz : x ∈ openSegment ℝ y z
this✝ : (fun a => f a) '' openSegment ℝ y z = openSegment ℝ (f y) (f z)
this : f y = f x ∧ f z = f x
⊢ y = x ∧ z = x
tactic: have := hw.2 (mem_image_of_mem _ hy) (mem_image_of_mem _ hz) <| by
    rw [← this]; exact mem_image_of_mem _ hxyz
state_before: case intro.intro.intro
E : Type u_1
F : Type u_2
inst✝¹⁰ : AddCommGroup E
inst✝⁹ : Module ℝ E
inst✝⁸ : TopologicalSpace E
inst✝⁷ : T2Space E
inst✝⁶ : TopologicalAddGroup E
inst✝⁵ : ContinuousSMul ℝ E
inst✝⁴ : LocallyConvexSpace ℝ E
s : Set E
inst✝³ : AddCommGroup F
inst✝² : Module ℝ F
inst✝¹ : TopologicalSpace F
inst✝ : T1Space F
f : E →ᴬ[ℝ] F
hs : IsCompact s
x : E
hx : x ∈ s
hw : f x ∈ extremePoints ℝ (⇑f '' s)
ht : IsCompact {x_1 | x_1 ∈ s ∧ f x_1 = f x}
ht₀ : {x_1 | x_1 ∈ s ∧ f x_1 = f x}.Nonempty
hyt :
  ∀ ⦃x₁ : E⦄,
    x₁ ∈ {x_1 | x_1 ∈ s ∧ f x_1 = f x} →
      ∀ ⦃x₂ : E⦄, x₂ ∈ {x_1 | x_1 ∈ s ∧ f x_1 = f x} → x ∈ openSegment ℝ x₁ x₂ → x₁ = x ∧ x₂ = x
y : E
hy : y ∈ s
z : E
hz : z ∈ s
hxyz : x ∈ openSegment ℝ y z
this✝ : (fun a => f a) '' openSegment ℝ y z = openSegment ℝ (f y) (f z)
this : f y = f x ∧ f z = f x
⊢ y = x ∧ z = x
state_after: no goals
tactic: exact hyt ⟨hy, this.1⟩ ⟨hz, this.2⟩ hxyz