l3lab/ntp-mathlib huggingface dataset:
/-- The distance from the orthocenter to the reflection of the
circumcenter in a side equals the circumradius. -/
theorem dist_orthocenter_reflection_circumcenter (t : Triangle ℝ P) {i₁ i₂ : Fin 3} (h : i₁ ≠ i₂) :
    dist t.orthocenter (reflection (affineSpan ℝ (t.points '' {i₁, i₂})) t.circumcenter) =
      t.circumradius := by
  rw [← mul_self_inj_of_nonneg dist_nonneg t.circumradius_nonneg,
    t.reflection_circumcenter_eq_affineCombination_of_pointsWithCircumcenter h,
    t.orthocenter_eq_mongePoint, mongePoint_eq_affineCombination_of_pointsWithCircumcenter,
    dist_affineCombination t.pointsWithCircumcenter (sum_mongePointWeightsWithCircumcenter _)
      (sum_reflectionCircumcenterWeightsWithCircumcenter h)]
  simp_rw [sum_pointsWithCircumcenter, Pi.sub_apply, mongePointWeightsWithCircumcenter,
    reflectionCircumcenterWeightsWithCircumcenter]
  

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
i₁ i₂ : Fin 3
h : i₁ ≠ i₂
⊢ -(∑ x : Fin (0 + 2 + 1),
            (∑ x_1 : Fin (0 + 2 + 1),
                ((↑(0 + 1))⁻¹ - if x = i₁ ∨ x = i₂ then 1 else 0) *
                    ((↑(0 + 1))⁻¹ - if x_1 = i₁ ∨ x_1 = i₂ then 1 else 0) *
                  (dist (pointsWithCircumcenter t (PointsWithCircumcenterIndex.pointIndex x))
                      (pointsWithCircumcenter t (PointsWithCircumcenterIndex.pointIndex x_1)) *
                    dist (pointsWithCircumcenter t (PointsWithCircumcenterIndex.pointIndex x))
                      (pointsWithCircumcenter t (PointsWithCircumcenterIndex.pointIndex x_1))) +
              ((↑(0 + 1))⁻¹ - if x = i₁ ∨ x = i₂ then 1 else 0) * (-2 / ↑(0 + 1) - -1) *
                (dist (pointsWithCircumcenter t (PointsWithCircumcenterIndex.pointIndex x))
                    (pointsWithCircumcenter t PointsWithCircumcenterIndex.circumcenterIndex) *
                  dist (pointsWithCircumcenter t (PointsWithCircumcenterIndex.pointIndex x))
                    (pointsWithCircumcenter t PointsWithCircumcenterIndex.circumcenterIndex))) +
          (∑ x : Fin (0 + 2 + 1),
              (-2 / ↑(0 + 1) - -1) * ((↑(0 + 1))⁻¹ - if x = i₁ ∨ x = i₂ then 1 else 0) *
                (dist (pointsWithCircumcenter t PointsWithCircumcenterIndex.circumcenterIndex)
                    (pointsWithCircumcenter t (PointsWithCircumcenterIndex.pointIndex x)) *
                  dist (pointsWithCircumcenter t PointsWithCircumcenterIndex.circumcenterIndex)
                    (pointsWithCircumcenter t (PointsWithCircumcenterIndex.pointIndex x))) +
            (-2 / ↑(0 + 1) - -1) * (-2 / ↑(0 + 1) - -1) *
              (dist (pointsWithCircumcenter t PointsWithCircumcenterIndex.circumcenterIndex)
                  (pointsWithCircumcenter t PointsWithCircumcenterIndex.circumcenterIndex) *
                dist (pointsWithCircumcenter t PointsWithCircumcenterIndex.circumcenterIndex)
                  (pointsWithCircumcenter t PointsWithCircumcenterIndex.circumcenterIndex)))) /
      2 =
    circumradius t * circumradius t

Next tactic:
have hu : ({i₁, i₂} : Finset (Fin 3)) ⊆ univ := subset_univ _
/-- The distance from the orthocenter to the reflection of the
circumcenter in a side equals the circumradius. -/
theorem dist_orthocenter_reflection_circumcenter (t : Triangle ℝ P) {i₁ i₂ : Fin 3} (h : i₁ ≠ i₂) :
    dist t.orthocenter (reflection (affineSpan ℝ (t.points '' {i₁, i₂})) t.circumcenter) =
      t.circumradius := by
  rw [← mul_self_inj_of_nonneg dist_nonneg t.circumradius_nonneg,
    t.reflection_circumcenter_eq_affineCombination_of_pointsWithCircumcenter h,
    t.orthocenter_eq_mongePoint, mongePoint_eq_affineCombination_of_pointsWithCircumcenter,
    dist_affineCombination t.pointsWithCircumcenter (sum_mongePointWeightsWithCircumcenter _)
      (sum_reflectionCircumcenterWeightsWithCircumcenter h)]
  simp_rw [sum_pointsWithCircumcenter, Pi.sub_apply, mongePointWeightsWithCircumcenter,
    reflectionCircumcenterWeightsWithCircumcenter]
  have hu : ({i₁, i₂} : Finset (Fin 3)) ⊆ univ := subset_univ _
  obtain ⟨i₃, hi₃, hi₃₁, hi₃₂⟩ :
      ∃ i₃, univ \ ({i₁, i₂} : Finset (Fin 3)) = {i₃} ∧ i₃ ≠ i₁ ∧ i₃ ≠ i₂ := by
    -- porting note: was `decide!`
    

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
i₁ i₂ : Fin 3
h : i₁ ≠ i₂
hu : {i₁, i₂} ⊆ univ
⊢ ∃ i₃, univ \ {i₁, i₂} = {i₃} ∧ i₃ ≠ i₁ ∧ i₃ ≠ i₂

Next tactic:
fin_cases i₁
/-- The distance from the orthocenter to the reflection of the
circumcenter in a side equals the circumradius. -/
theorem dist_orthocenter_reflection_circumcenter (t : Triangle ℝ P) {i₁ i₂ : Fin 3} (h : i₁ ≠ i₂) :
    dist t.orthocenter (reflection (affineSpan ℝ (t.points '' {i₁, i₂})) t.circumcenter) =
      t.circumradius := by
  rw [← mul_self_inj_of_nonneg dist_nonneg t.circumradius_nonneg,
    t.reflection_circumcenter_eq_affineCombination_of_pointsWithCircumcenter h,
    t.orthocenter_eq_mongePoint, mongePoint_eq_affineCombination_of_pointsWithCircumcenter,
    dist_affineCombination t.pointsWithCircumcenter (sum_mongePointWeightsWithCircumcenter _)
      (sum_reflectionCircumcenterWeightsWithCircumcenter h)]
  simp_rw [sum_pointsWithCircumcenter, Pi.sub_apply, mongePointWeightsWithCircumcenter,
    reflectionCircumcenterWeightsWithCircumcenter]
  have hu : ({i₁, i₂} : Finset (Fin 3)) ⊆ univ := subset_univ _
  obtain ⟨i₃, hi₃, hi₃₁, hi₃₂⟩ :
      ∃ i₃, univ \ ({i₁, i₂} : Finset (Fin 3)) = {i₃} ∧ i₃ ≠ i₁ ∧ i₃ ≠ i₂ := by
    -- porting note: was `decide!`
    fin_cases i₁ <;> 

Proof state:
case head
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
i₂ : Fin 3
h : { val := 0, isLt := (_ : 0 < 3) } ≠ i₂
hu : {{ val := 0, isLt := (_ : 0 < 3) }, i₂} ⊆ univ
⊢ ∃ i₃, univ \ {{ val := 0, isLt := (_ : 0 < 3) }, i₂} = {i₃} ∧ i₃ ≠ { val := 0, isLt := (_ : 0 < 3) } ∧ i₃ ≠ i₂

Next tactic:
fin_cases i₂
/-- The distance from the orthocenter to the reflection of the
circumcenter in a side equals the circumradius. -/
theorem dist_orthocenter_reflection_circumcenter (t : Triangle ℝ P) {i₁ i₂ : Fin 3} (h : i₁ ≠ i₂) :
    dist t.orthocenter (reflection (affineSpan ℝ (t.points '' {i₁, i₂})) t.circumcenter) =
      t.circumradius := by
  rw [← mul_self_inj_of_nonneg dist_nonneg t.circumradius_nonneg,
    t.reflection_circumcenter_eq_affineCombination_of_pointsWithCircumcenter h,
    t.orthocenter_eq_mongePoint, mongePoint_eq_affineCombination_of_pointsWithCircumcenter,
    dist_affineCombination t.pointsWithCircumcenter (sum_mongePointWeightsWithCircumcenter _)
      (sum_reflectionCircumcenterWeightsWithCircumcenter h)]
  simp_rw [sum_pointsWithCircumcenter, Pi.sub_apply, mongePointWeightsWithCircumcenter,
    reflectionCircumcenterWeightsWithCircumcenter]
  have hu : ({i₁, i₂} : Finset (Fin 3)) ⊆ univ := subset_univ _
  obtain ⟨i₃, hi₃, hi₃₁, hi₃₂⟩ :
      ∃ i₃, univ \ ({i₁, i₂} : Finset (Fin 3)) = {i₃} ∧ i₃ ≠ i₁ ∧ i₃ ≠ i₂ := by
    -- porting note: was `decide!`
    fin_cases i₁ <;> 

Proof state:
case tail.head
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
i₂ : Fin 3
h : { val := 1, isLt := (_ : (fun a => a < 3) 1) } ≠ i₂
hu : {{ val := 1, isLt := (_ : (fun a => a < 3) 1) }, i₂} ⊆ univ
⊢ ∃ i₃,
    univ \ {{ val := 1, isLt := (_ : (fun a => a < 3) 1) }, i₂} = {i₃} ∧
      i₃ ≠ { val := 1, isLt := (_ : (fun a => a < 3) 1) } ∧ i₃ ≠ i₂

Next tactic:
fin_cases i₂
/-- The distance from the orthocenter to the reflection of the
circumcenter in a side equals the circumradius. -/
theorem dist_orthocenter_reflection_circumcenter (t : Triangle ℝ P) {i₁ i₂ : Fin 3} (h : i₁ ≠ i₂) :
    dist t.orthocenter (reflection (affineSpan ℝ (t.points '' {i₁, i₂})) t.circumcenter) =
      t.circumradius := by
  rw [← mul_self_inj_of_nonneg dist_nonneg t.circumradius_nonneg,
    t.reflection_circumcenter_eq_affineCombination_of_pointsWithCircumcenter h,
    t.orthocenter_eq_mongePoint, mongePoint_eq_affineCombination_of_pointsWithCircumcenter,
    dist_affineCombination t.pointsWithCircumcenter (sum_mongePointWeightsWithCircumcenter _)
      (sum_reflectionCircumcenterWeightsWithCircumcenter h)]
  simp_rw [sum_pointsWithCircumcenter, Pi.sub_apply, mongePointWeightsWithCircumcenter,
    reflectionCircumcenterWeightsWithCircumcenter]
  have hu : ({i₁, i₂} : Finset (Fin 3)) ⊆ univ := subset_univ _
  obtain ⟨i₃, hi₃, hi₃₁, hi₃₂⟩ :
      ∃ i₃, univ \ ({i₁, i₂} : Finset (Fin 3)) = {i₃} ∧ i₃ ≠ i₁ ∧ i₃ ≠ i₂ := by
    -- porting note: was `decide!`
    fin_cases i₁ <;> 

Proof state:
case tail.tail.head
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
i₂ : Fin 3
h : { val := 2, isLt := (_ : (fun a => (fun a => a < 3) a) 2) } ≠ i₂
hu : {{ val := 2, isLt := (_ : (fun a => (fun a => a < 3) a) 2) }, i₂} ⊆ univ
⊢ ∃ i₃,
    univ \ {{ val := 2, isLt := (_ : (fun a => (fun a => a < 3) a) 2) }, i₂} = {i₃} ∧
      i₃ ≠ { val := 2, isLt := (_ : (fun a => (fun a => a < 3) a) 2) } ∧ i₃ ≠ i₂

Next tactic:
fin_cases i₂
/-- The distance from the orthocenter to the reflection of the
circumcenter in a side equals the circumradius. -/
theorem dist_orthocenter_reflection_circumcenter (t : Triangle ℝ P) {i₁ i₂ : Fin 3} (h : i₁ ≠ i₂) :
    dist t.orthocenter (reflection (affineSpan ℝ (t.points '' {i₁, i₂})) t.circumcenter) =
      t.circumradius := by
  rw [← mul_self_inj_of_nonneg dist_nonneg t.circumradius_nonneg,
    t.reflection_circumcenter_eq_affineCombination_of_pointsWithCircumcenter h,
    t.orthocenter_eq_mongePoint, mongePoint_eq_affineCombination_of_pointsWithCircumcenter,
    dist_affineCombination t.pointsWithCircumcenter (sum_mongePointWeightsWithCircumcenter _)
      (sum_reflectionCircumcenterWeightsWithCircumcenter h)]
  simp_rw [sum_pointsWithCircumcenter, Pi.sub_apply, mongePointWeightsWithCircumcenter,
    reflectionCircumcenterWeightsWithCircumcenter]
  have hu : ({i₁, i₂} : Finset (Fin 3)) ⊆ univ := subset_univ _
  obtain ⟨i₃, hi₃, hi₃₁, hi₃₂⟩ :
      ∃ i₃, univ \ ({i₁, i₂} : Finset (Fin 3)) = {i₃} ∧ i₃ ≠ i₁ ∧ i₃ ≠ i₂ := by
    -- porting note: was `decide!`
    fin_cases i₁ <;> fin_cases i₂ <;> 

Proof state:
case head.head
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
h : { val := 0, isLt := (_ : 0 < 3) } ≠ { val := 0, isLt := (_ : 0 < 3) }
hu : {{ val := 0, isLt := (_ : 0 < 3) }, { val := 0, isLt := (_ : 0 < 3) }} ⊆ univ
⊢ ∃ i₃,
    univ \ {{ val := 0, isLt := (_ : 0 < 3) }, { val := 0, isLt := (_ : 0 < 3) }} = {i₃} ∧
      i₃ ≠ { val := 0, isLt := (_ : 0 < 3) } ∧ i₃ ≠ { val := 0, isLt := (_ : 0 < 3) }

Next tactic:
simp at h
/-- The distance from the orthocenter to the reflection of the
circumcenter in a side equals the circumradius. -/
theorem dist_orthocenter_reflection_circumcenter (t : Triangle ℝ P) {i₁ i₂ : Fin 3} (h : i₁ ≠ i₂) :
    dist t.orthocenter (reflection (affineSpan ℝ (t.points '' {i₁, i₂})) t.circumcenter) =
      t.circumradius := by
  rw [← mul_self_inj_of_nonneg dist_nonneg t.circumradius_nonneg,
    t.reflection_circumcenter_eq_affineCombination_of_pointsWithCircumcenter h,
    t.orthocenter_eq_mongePoint, mongePoint_eq_affineCombination_of_pointsWithCircumcenter,
    dist_affineCombination t.pointsWithCircumcenter (sum_mongePointWeightsWithCircumcenter _)
      (sum_reflectionCircumcenterWeightsWithCircumcenter h)]
  simp_rw [sum_pointsWithCircumcenter, Pi.sub_apply, mongePointWeightsWithCircumcenter,
    reflectionCircumcenterWeightsWithCircumcenter]
  have hu : ({i₁, i₂} : Finset (Fin 3)) ⊆ univ := subset_univ _
  obtain ⟨i₃, hi₃, hi₃₁, hi₃₂⟩ :
      ∃ i₃, univ \ ({i₁, i₂} : Finset (Fin 3)) = {i₃} ∧ i₃ ≠ i₁ ∧ i₃ ≠ i₂ := by
    -- porting note: was `decide!`
    fin_cases i₁ <;> fin_cases i₂ <;> 

Proof state:
case head.tail.head
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
h : { val := 0, isLt := (_ : 0 < 3) } ≠ { val := 1, isLt := (_ : (fun a => a < 3) 1) }
hu : {{ val := 0, isLt := (_ : 0 < 3) }, { val := 1, isLt := (_ : (fun a => a < 3) 1) }} ⊆ univ
⊢ ∃ i₃,
    univ \ {{ val := 0, isLt := (_ : 0 < 3) }, { val := 1, isLt := (_ : (fun a => a < 3) 1) }} = {i₃} ∧
      i₃ ≠ { val := 0, isLt := (_ : 0 < 3) } ∧ i₃ ≠ { val := 1, isLt := (_ : (fun a => a < 3) 1) }

Next tactic:
simp at h
/-- The distance from the orthocenter to the reflection of the
circumcenter in a side equals the circumradius. -/
theorem dist_orthocenter_reflection_circumcenter (t : Triangle ℝ P) {i₁ i₂ : Fin 3} (h : i₁ ≠ i₂) :
    dist t.orthocenter (reflection (affineSpan ℝ (t.points '' {i₁, i₂})) t.circumcenter) =
      t.circumradius := by
  rw [← mul_self_inj_of_nonneg dist_nonneg t.circumradius_nonneg,
    t.reflection_circumcenter_eq_affineCombination_of_pointsWithCircumcenter h,
    t.orthocenter_eq_mongePoint, mongePoint_eq_affineCombination_of_pointsWithCircumcenter,
    dist_affineCombination t.pointsWithCircumcenter (sum_mongePointWeightsWithCircumcenter _)
      (sum_reflectionCircumcenterWeightsWithCircumcenter h)]
  simp_rw [sum_pointsWithCircumcenter, Pi.sub_apply, mongePointWeightsWithCircumcenter,
    reflectionCircumcenterWeightsWithCircumcenter]
  have hu : ({i₁, i₂} : Finset (Fin 3)) ⊆ univ := subset_univ _
  obtain ⟨i₃, hi₃, hi₃₁, hi₃₂⟩ :
      ∃ i₃, univ \ ({i₁, i₂} : Finset (Fin 3)) = {i₃} ∧ i₃ ≠ i₁ ∧ i₃ ≠ i₂ := by
    -- porting note: was `decide!`
    fin_cases i₁ <;> fin_cases i₂ <;> 

Proof state:
case head.tail.tail.head
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
h : { val := 0, isLt := (_ : 0 < 3) } ≠ { val := 2, isLt := (_ : (fun a => (fun a => a < 3) a) 2) }
hu : {{ val := 0, isLt := (_ : 0 < 3) }, { val := 2, isLt := (_ : (fun a => (fun a => a < 3) a) 2) }} ⊆ univ
⊢ ∃ i₃,
    univ \ {{ val := 0, isLt := (_ : 0 < 3) }, { val := 2, isLt := (_ : (fun a => (fun a => a < 3) a) 2) }} = {i₃} ∧
      i₃ ≠ { val := 0, isLt := (_ : 0 < 3) } ∧ i₃ ≠ { val := 2, isLt := (_ : (fun a => (fun a => a < 3) a) 2) }

Next tactic:
simp at h
/-- The distance from the orthocenter to the reflection of the
circumcenter in a side equals the circumradius. -/
theorem dist_orthocenter_reflection_circumcenter (t : Triangle ℝ P) {i₁ i₂ : Fin 3} (h : i₁ ≠ i₂) :
    dist t.orthocenter (reflection (affineSpan ℝ (t.points '' {i₁, i₂})) t.circumcenter) =
      t.circumradius := by
  rw [← mul_self_inj_of_nonneg dist_nonneg t.circumradius_nonneg,
    t.reflection_circumcenter_eq_affineCombination_of_pointsWithCircumcenter h,
    t.orthocenter_eq_mongePoint, mongePoint_eq_affineCombination_of_pointsWithCircumcenter,
    dist_affineCombination t.pointsWithCircumcenter (sum_mongePointWeightsWithCircumcenter _)
      (sum_reflectionCircumcenterWeightsWithCircumcenter h)]
  simp_rw [sum_pointsWithCircumcenter, Pi.sub_apply, mongePointWeightsWithCircumcenter,
    reflectionCircumcenterWeightsWithCircumcenter]
  have hu : ({i₁, i₂} : Finset (Fin 3)) ⊆ univ := subset_univ _
  obtain ⟨i₃, hi₃, hi₃₁, hi₃₂⟩ :
      ∃ i₃, univ \ ({i₁, i₂} : Finset (Fin 3)) = {i₃} ∧ i₃ ≠ i₁ ∧ i₃ ≠ i₂ := by
    -- porting note: was `decide!`
    fin_cases i₁ <;> fin_cases i₂ <;> 

Proof state:
case tail.head.head
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
h : { val := 1, isLt := (_ : (fun a => a < 3) 1) } ≠ { val := 0, isLt := (_ : 0 < 3) }
hu : {{ val := 1, isLt := (_ : (fun a => a < 3) 1) }, { val := 0, isLt := (_ : 0 < 3) }} ⊆ univ
⊢ ∃ i₃,
    univ \ {{ val := 1, isLt := (_ : (fun a => a < 3) 1) }, { val := 0, isLt := (_ : 0 < 3) }} = {i₃} ∧
      i₃ ≠ { val := 1, isLt := (_ : (fun a => a < 3) 1) } ∧ i₃ ≠ { val := 0, isLt := (_ : 0 < 3) }

Next tactic:
simp at h
/-- The distance from the orthocenter to the reflection of the
circumcenter in a side equals the circumradius. -/
theorem dist_orthocenter_reflection_circumcenter (t : Triangle ℝ P) {i₁ i₂ : Fin 3} (h : i₁ ≠ i₂) :
    dist t.orthocenter (reflection (affineSpan ℝ (t.points '' {i₁, i₂})) t.circumcenter) =
      t.circumradius := by
  rw [← mul_self_inj_of_nonneg dist_nonneg t.circumradius_nonneg,
    t.reflection_circumcenter_eq_affineCombination_of_pointsWithCircumcenter h,
    t.orthocenter_eq_mongePoint, mongePoint_eq_affineCombination_of_pointsWithCircumcenter,
    dist_affineCombination t.pointsWithCircumcenter (sum_mongePointWeightsWithCircumcenter _)
      (sum_reflectionCircumcenterWeightsWithCircumcenter h)]
  simp_rw [sum_pointsWithCircumcenter, Pi.sub_apply, mongePointWeightsWithCircumcenter,
    reflectionCircumcenterWeightsWithCircumcenter]
  have hu : ({i₁, i₂} : Finset (Fin 3)) ⊆ univ := subset_univ _
  obtain ⟨i₃, hi₃, hi₃₁, hi₃₂⟩ :
      ∃ i₃, univ \ ({i₁, i₂} : Finset (Fin 3)) = {i₃} ∧ i₃ ≠ i₁ ∧ i₃ ≠ i₂ := by
    -- porting note: was `decide!`
    fin_cases i₁ <;> fin_cases i₂ <;> 

Proof state:
case tail.head.tail.head
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
h : { val := 1, isLt := (_ : (fun a => a < 3) 1) } ≠ { val := 1, isLt := (_ : (fun a => a < 3) 1) }
hu : {{ val := 1, isLt := (_ : (fun a => a < 3) 1) }, { val := 1, isLt := (_ : (fun a => a < 3) 1) }} ⊆ univ
⊢ ∃ i₃,
    univ \ {{ val := 1, isLt := (_ : (fun a => a < 3) 1) }, { val := 1, isLt := (_ : (fun a => a < 3) 1) }} = {i₃} ∧
      i₃ ≠ { val := 1, isLt := (_ : (fun a => a < 3) 1) } ∧ i₃ ≠ { val := 1, isLt := (_ : (fun a => a < 3) 1) }

Next tactic:
simp at h
/-- The distance from the orthocenter to the reflection of the
circumcenter in a side equals the circumradius. -/
theorem dist_orthocenter_reflection_circumcenter (t : Triangle ℝ P) {i₁ i₂ : Fin 3} (h : i₁ ≠ i₂) :
    dist t.orthocenter (reflection (affineSpan ℝ (t.points '' {i₁, i₂})) t.circumcenter) =
      t.circumradius := by
  rw [← mul_self_inj_of_nonneg dist_nonneg t.circumradius_nonneg,
    t.reflection_circumcenter_eq_affineCombination_of_pointsWithCircumcenter h,
    t.orthocenter_eq_mongePoint, mongePoint_eq_affineCombination_of_pointsWithCircumcenter,
    dist_affineCombination t.pointsWithCircumcenter (sum_mongePointWeightsWithCircumcenter _)
      (sum_reflectionCircumcenterWeightsWithCircumcenter h)]
  simp_rw [sum_pointsWithCircumcenter, Pi.sub_apply, mongePointWeightsWithCircumcenter,
    reflectionCircumcenterWeightsWithCircumcenter]
  have hu : ({i₁, i₂} : Finset (Fin 3)) ⊆ univ := subset_univ _
  obtain ⟨i₃, hi₃, hi₃₁, hi₃₂⟩ :
      ∃ i₃, univ \ ({i₁, i₂} : Finset (Fin 3)) = {i₃} ∧ i₃ ≠ i₁ ∧ i₃ ≠ i₂ := by
    -- porting note: was `decide!`
    fin_cases i₁ <;> fin_cases i₂ <;> 

Proof state:
case tail.head.tail.tail.head
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
h : { val := 1, isLt := (_ : (fun a => a < 3) 1) } ≠ { val := 2, isLt := (_ : (fun a => (fun a => a < 3) a) 2) }
hu :
  {{ val := 1, isLt := (_ : (fun a => a < 3) 1) }, { val := 2, isLt := (_ : (fun a => (fun a => a < 3) a) 2) }} ⊆ univ
⊢ ∃ i₃,
    univ \
          {{ val := 1, isLt := (_ : (fun a => a < 3) 1) },
            { val := 2, isLt := (_ : (fun a => (fun a => a < 3) a) 2) }} =
        {i₃} ∧
      i₃ ≠ { val := 1, isLt := (_ : (fun a => a < 3) 1) } ∧
        i₃ ≠ { val := 2, isLt := (_ : (fun a => (fun a => a < 3) a) 2) }

Next tactic:
simp at h
/-- The distance from the orthocenter to the reflection of the
circumcenter in a side equals the circumradius. -/
theorem dist_orthocenter_reflection_circumcenter (t : Triangle ℝ P) {i₁ i₂ : Fin 3} (h : i₁ ≠ i₂) :
    dist t.orthocenter (reflection (affineSpan ℝ (t.points '' {i₁, i₂})) t.circumcenter) =
      t.circumradius := by
  rw [← mul_self_inj_of_nonneg dist_nonneg t.circumradius_nonneg,
    t.reflection_circumcenter_eq_affineCombination_of_pointsWithCircumcenter h,
    t.orthocenter_eq_mongePoint, mongePoint_eq_affineCombination_of_pointsWithCircumcenter,
    dist_affineCombination t.pointsWithCircumcenter (sum_mongePointWeightsWithCircumcenter _)
      (sum_reflectionCircumcenterWeightsWithCircumcenter h)]
  simp_rw [sum_pointsWithCircumcenter, Pi.sub_apply, mongePointWeightsWithCircumcenter,
    reflectionCircumcenterWeightsWithCircumcenter]
  have hu : ({i₁, i₂} : Finset (Fin 3)) ⊆ univ := subset_univ _
  obtain ⟨i₃, hi₃, hi₃₁, hi₃₂⟩ :
      ∃ i₃, univ \ ({i₁, i₂} : Finset (Fin 3)) = {i₃} ∧ i₃ ≠ i₁ ∧ i₃ ≠ i₂ := by
    -- porting note: was `decide!`
    fin_cases i₁ <;> fin_cases i₂ <;> 

Proof state:
case tail.tail.head.head
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
h : { val := 2, isLt := (_ : (fun a => (fun a => a < 3) a) 2) } ≠ { val := 0, isLt := (_ : 0 < 3) }
hu : {{ val := 2, isLt := (_ : (fun a => (fun a => a < 3) a) 2) }, { val := 0, isLt := (_ : 0 < 3) }} ⊆ univ
⊢ ∃ i₃,
    univ \ {{ val := 2, isLt := (_ : (fun a => (fun a => a < 3) a) 2) }, { val := 0, isLt := (_ : 0 < 3) }} = {i₃} ∧
      i₃ ≠ { val := 2, isLt := (_ : (fun a => (fun a => a < 3) a) 2) } ∧ i₃ ≠ { val := 0, isLt := (_ : 0 < 3) }

Next tactic:
simp at h
/-- The distance from the orthocenter to the reflection of the
circumcenter in a side equals the circumradius. -/
theorem dist_orthocenter_reflection_circumcenter (t : Triangle ℝ P) {i₁ i₂ : Fin 3} (h : i₁ ≠ i₂) :
    dist t.orthocenter (reflection (affineSpan ℝ (t.points '' {i₁, i₂})) t.circumcenter) =
      t.circumradius := by
  rw [← mul_self_inj_of_nonneg dist_nonneg t.circumradius_nonneg,
    t.reflection_circumcenter_eq_affineCombination_of_pointsWithCircumcenter h,
    t.orthocenter_eq_mongePoint, mongePoint_eq_affineCombination_of_pointsWithCircumcenter,
    dist_affineCombination t.pointsWithCircumcenter (sum_mongePointWeightsWithCircumcenter _)
      (sum_reflectionCircumcenterWeightsWithCircumcenter h)]
  simp_rw [sum_pointsWithCircumcenter, Pi.sub_apply, mongePointWeightsWithCircumcenter,
    reflectionCircumcenterWeightsWithCircumcenter]
  have hu : ({i₁, i₂} : Finset (Fin 3)) ⊆ univ := subset_univ _
  obtain ⟨i₃, hi₃, hi₃₁, hi₃₂⟩ :
      ∃ i₃, univ \ ({i₁, i₂} : Finset (Fin 3)) = {i₃} ∧ i₃ ≠ i₁ ∧ i₃ ≠ i₂ := by
    -- porting note: was `decide!`
    fin_cases i₁ <;> fin_cases i₂ <;> 

Proof state:
case tail.tail.head.tail.head
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
h : { val := 2, isLt := (_ : (fun a => (fun a => a < 3) a) 2) } ≠ { val := 1, isLt := (_ : (fun a => a < 3) 1) }
hu :
  {{ val := 2, isLt := (_ : (fun a => (fun a => a < 3) a) 2) }, { val := 1, isLt := (_ : (fun a => a < 3) 1) }} ⊆ univ
⊢ ∃ i₃,
    univ \
          {{ val := 2, isLt := (_ : (fun a => (fun a => a < 3) a) 2) },
            { val := 1, isLt := (_ : (fun a => a < 3) 1) }} =
        {i₃} ∧
      i₃ ≠ { val := 2, isLt := (_ : (fun a => (fun a => a < 3) a) 2) } ∧
        i₃ ≠ { val := 1, isLt := (_ : (fun a => a < 3) 1) }

Next tactic:
simp at h