-- Mathlib/Geometry/Euclidean/MongePoint.lean
theorem exists_dist_eq_circumradius_of_subset_insert_orthocenter {t : Triangle ℝ P}
    (ho : t.orthocenter ∉ Set.range t.points) {p : Fin 3 → P}
    (hps : Set.range p ⊆ insert t.orthocenter (Set.range t.points)) (hpi : Function.Injective p) :
    ∃ c ∈ affineSpan ℝ (Set.range t.points), ∀ p₁ ∈ Set.range p, dist p₁ c = t.circumradius

Proof state:
case right.intro
V : Type u_1
P : Type u_2
inst✝³ : NormedAddCommGroup V
inst✝² : InnerProductSpace ℝ V
inst✝¹ : MetricSpace P
inst✝ : NormedAddTorsor V P
t : Triangle ℝ P
ho : t.orthocenter ∉ Set.range t.points
p : Fin 3 → P
hps : Set.range p ⊆ insert t.orthocenter (Set.range t.points)
hpi : Function.Injective p
hs : Set.range p = Set.range t.points
i : Fin (2 + 1)
⊢ dist (t.points i) (Simplex.circumcenter t) = Simplex.circumradius t

Tactic:
exact t.dist_circumcenter_eq_circumradius _

Result:
no goals

Proof state:
case inr
V : Type u_1
P : Type u_2
inst✝³ : NormedAddCommGroup V
inst✝² : InnerProductSpace ℝ V
inst✝¹ : MetricSpace P
inst✝ : NormedAddTorsor V P
t : Triangle ℝ P
ho : t.orthocenter ∉ Set.range t.points
p : Fin 3 → P
hps : Set.range p ⊆ insert t.orthocenter (Set.range t.points)
hpi : Function.Injective p
hs : Set.range p = Set.range t.points
⊢ ∃ c ∈ affineSpan ℝ (Set.range t.points), ∀ p₁ ∈ Set.range p, dist p₁ c = Simplex.circumradius t

Tactic:
use t.circumcenter, t.circumcenter_mem_affineSpan

Result:
case right
V : Type u_1
P : Type u_2
inst✝³ : NormedAddCommGroup V
inst✝² : InnerProductSpace ℝ V
inst✝¹ : MetricSpace P
inst✝ : NormedAddTorsor V P
t : Triangle ℝ P
ho : t.orthocenter ∉ Set.range t.points
p : Fin 3 → P
hps : Set.range p ⊆ insert t.orthocenter (Set.range t.points)
hpi : Function.Injective p
hs : Set.range p = Set.range t.points
⊢ ∀ p₁ ∈ Set.range p, dist p₁ (Simplex.circumcenter t) = Simplex.circumradius t

Proof state:
V : Type u_1
P : Type u_2
inst✝³ : NormedAddCommGroup V
inst✝² : InnerProductSpace ℝ V
inst✝¹ : MetricSpace P
inst✝ : NormedAddTorsor V P
t : Triangle ℝ P
ho : t.orthocenter ∉ Set.range t.points
p : Fin 3 → P
hps : Set.range p ⊆ insert t.orthocenter (Set.range t.points)
hpi : Function.Injective p
⊢ ∃ c ∈ affineSpan ℝ (Set.range t.points), ∀ p₁ ∈ Set.range p, dist p₁ c = Simplex.circumradius t

Tactic:
rcases exists_of_range_subset_orthocentricSystem ho hps hpi with
  (⟨i₁, i₂, i₃, j₂, j₃, _, _, _, h₁₂₃, h₁, hj₂₃, h₂, h₃⟩ | hs)

Result:
case inl.intro.intro.intro.intro.intro.intro.intro.intro.intro.intro.intro.intro
V : Type u_1
P : Type u_2
inst✝³ : NormedAddCommGroup V
inst✝² : InnerProductSpace ℝ V
inst✝¹ : MetricSpace P
inst✝ : NormedAddTorsor V P
t : Triangle ℝ P
ho : t.orthocenter ∉ Set.range t.points
p : Fin 3 → P
hps : Set.range p ⊆ insert t.orthocenter (Set.range t.points)
hpi : Function.Injective p
i₁ i₂ i₃ j₂ j₃ : Fin 3
left✝² : i₁ ≠ i₂
left✝¹ : i₁ ≠ i₃
left✝ : i₂ ≠ i₃
h₁₂₃ : ∀ (i : Fin 3), i = i₁ ∨ i = i₂ ∨ i = i₃
h₁ : p i₁ = t.orthocenter
hj₂₃ : j₂ ≠ j₃
h₂ : t.points j₂ = p i₂
h₃ : t.points j₃ = p i₃
⊢ ∃ c ∈ affineSpan ℝ (Set.range t.points), ∀ p₁ ∈ Set.range p, dist p₁ c = Simplex.circumradius t

case inr
V : Type u_1
P : Type u_2
inst✝³ : NormedAddCommGroup V
inst✝² : InnerProductSpace ℝ V
inst✝¹ : MetricSpace P
inst✝ : NormedAddTorsor V P
t : Triangle ℝ P
ho : t.orthocenter ∉ Set.range t.points
p : Fin 3 → P
hps : Set.range p ⊆ insert t.orthocenter (Set.range t.points)
hpi : Function.Injective p
hs : Set.range p = Set.range t.points
⊢ ∃ c ∈ affineSpan ℝ (Set.range t.points), ∀ p₁ ∈ Set.range p, dist p₁ c = Simplex.circumradius t

Proof state:
case right.intro.inr.inl.refl
V : Type u_1
P : Type u_2
inst✝³ : NormedAddCommGroup V
inst✝² : InnerProductSpace ℝ V
inst✝¹ : MetricSpace P
inst✝ : NormedAddTorsor V P
t : Triangle ℝ P
ho : t.orthocenter ∉ Set.range t.points
p : Fin 3 → P
hps : Set.range p ⊆ insert t.orthocenter (Set.range t.points)
hpi : Function.Injective p
i₁ i₂ i₃ j₂ j₃ : Fin 3
left✝² : i₁ ≠ i₂
left✝¹ : i₁ ≠ i₃
left✝ : i₂ ≠ i₃
h₁₂₃ : ∀ (i : Fin 3), i = i₁ ∨ i = i₂ ∨ i = i₃
h₁ : p i₁ = t.orthocenter
hj₂₃ : j₂ ≠ j₃
h₂ : t.points j₂ = p i₂
h₃ : t.points j₃ = p i₃
⊢ dist (t.points j₂) (Simplex.circumcenter t) = Simplex.circumradius t

Tactic:
exact t.dist_circumcenter_eq_circumradius _

Result:
no goals

Proof state:
case right
V : Type u_1
P : Type u_2
inst✝³ : NormedAddCommGroup V
inst✝² : InnerProductSpace ℝ V
inst✝¹ : MetricSpace P
inst✝ : NormedAddTorsor V P
t : Triangle ℝ P
ho : t.orthocenter ∉ Set.range t.points
p : Fin 3 → P
hps : Set.range p ⊆ insert t.orthocenter (Set.range t.points)
hpi : Function.Injective p
hs : Set.range p = Set.range t.points
p₁ : P
hp₁ : p₁ ∈ Set.range t.points
⊢ dist p₁ (Simplex.circumcenter t) = Simplex.circumradius t

Tactic:
rcases hp₁ with ⟨i, rfl⟩

Result:
case right.intro
V : Type u_1
P : Type u_2
inst✝³ : NormedAddCommGroup V
inst✝² : InnerProductSpace ℝ V
inst✝¹ : MetricSpace P
inst✝ : NormedAddTorsor V P
t : Triangle ℝ P
ho : t.orthocenter ∉ Set.range t.points
p : Fin 3 → P
hps : Set.range p ⊆ insert t.orthocenter (Set.range t.points)
hpi : Function.Injective p
hs : Set.range p = Set.range t.points
i : Fin (2 + 1)
⊢ dist (t.points i) (Simplex.circumcenter t) = Simplex.circumradius t

Proof state:
case right
V : Type u_1
P : Type u_2
inst✝³ : NormedAddCommGroup V
inst✝² : InnerProductSpace ℝ V
inst✝¹ : MetricSpace P
inst✝ : NormedAddTorsor V P
t : Triangle ℝ P
ho : t.orthocenter ∉ Set.range t.points
p : Fin 3 → P
hps : Set.range p ⊆ insert t.orthocenter (Set.range t.points)
hpi : Function.Injective p
hs : Set.range p = Set.range t.points
⊢ ∀ p₁ ∈ Set.range p, dist p₁ (Simplex.circumcenter t) = Simplex.circumradius t

Tactic:
intro p₁ hp₁

Result:
case right
V : Type u_1
P : Type u_2
inst✝³ : NormedAddCommGroup V
inst✝² : InnerProductSpace ℝ V
inst✝¹ : MetricSpace P
inst✝ : NormedAddTorsor V P
t : Triangle ℝ P
ho : t.orthocenter ∉ Set.range t.points
p : Fin 3 → P
hps : Set.range p ⊆ insert t.orthocenter (Set.range t.points)
hpi : Function.Injective p
hs : Set.range p = Set.range t.points
p₁ : P
hp₁ : p₁ ∈ Set.range p
⊢ dist p₁ (Simplex.circumcenter t) = Simplex.circumradius t