Theorem: IsometryEquiv.map_midpoint
File: Mathlib/Analysis/NormedSpace/MazurUlam.lean

Proof steps:
state_before: E : Type u_1
PE : Type u_2
F : Type u_3
PF : Type u_4
inst✝⁷ : NormedAddCommGroup E
inst✝⁶ : NormedSpace ℝ E
inst✝⁵ : MetricSpace PE
inst✝⁴ : NormedAddTorsor E PE
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace ℝ F
inst✝¹ : MetricSpace PF
inst✝ : NormedAddTorsor F PF
f : PE ≃ᵢ PF
x y : PE
⊢ f (midpoint ℝ x y) = midpoint ℝ (f x) (f y)
state_after: E : Type u_1
PE : Type u_2
F : Type u_3
PF : Type u_4
inst✝⁷ : NormedAddCommGroup E
inst✝⁶ : NormedSpace ℝ E
inst✝⁵ : MetricSpace PE
inst✝⁴ : NormedAddTorsor E PE
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace ℝ F
inst✝¹ : MetricSpace PF
inst✝ : NormedAddTorsor F PF
f : PE ≃ᵢ PF
x y : PE
e : PE ≃ᵢ PE :=
  ((f.trans (pointReflection ℝ (midpoint ℝ (f x) (f y))).toIsometryEquiv).trans f.symm).trans
    (pointReflection ℝ (midpoint ℝ x y)).toIsometryEquiv
⊢ f (midpoint ℝ x y) = midpoint ℝ (f x) (f y)
tactic: set e : PE ≃ᵢ PE :=
    ((f.trans <| (pointReflection ℝ <| midpoint ℝ (f x) (f y)).toIsometryEquiv).trans f.symm).trans
      (pointReflection ℝ <| midpoint ℝ x y).toIsometryEquiv
state_before: E : Type u_1
PE : Type u_2
F : Type u_3
PF : Type u_4
inst✝⁷ : NormedAddCommGroup E
inst✝⁶ : NormedSpace ℝ E
inst✝⁵ : MetricSpace PE
inst✝⁴ : NormedAddTorsor E PE
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace ℝ F
inst✝¹ : MetricSpace PF
inst✝ : NormedAddTorsor F PF
f : PE ≃ᵢ PF
x y : PE
e : PE ≃ᵢ PE :=
  ((f.trans (pointReflection ℝ (midpoint ℝ (f x) (f y))).toIsometryEquiv).trans f.symm).trans
    (pointReflection ℝ (midpoint ℝ x y)).toIsometryEquiv
⊢ f (midpoint ℝ x y) = midpoint ℝ (f x) (f y)
state_after: E : Type u_1
PE : Type u_2
F : Type u_3
PF : Type u_4
inst✝⁷ : NormedAddCommGroup E
inst✝⁶ : NormedSpace ℝ E
inst✝⁵ : MetricSpace PE
inst✝⁴ : NormedAddTorsor E PE
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace ℝ F
inst✝¹ : MetricSpace PF
inst✝ : NormedAddTorsor F PF
f : PE ≃ᵢ PF
x y : PE
e : PE ≃ᵢ PE :=
  ((f.trans (pointReflection ℝ (midpoint ℝ (f x) (f y))).toIsometryEquiv).trans f.symm).trans
    (pointReflection ℝ (midpoint ℝ x y)).toIsometryEquiv
hx : e x = x
⊢ f (midpoint ℝ x y) = midpoint ℝ (f x) (f y)
tactic: have hx : e x = x := by simp [e]
state_before: E : Type u_1
PE : Type u_2
F : Type u_3
PF : Type u_4
inst✝⁷ : NormedAddCommGroup E
inst✝⁶ : NormedSpace ℝ E
inst✝⁵ : MetricSpace PE
inst✝⁴ : NormedAddTorsor E PE
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace ℝ F
inst✝¹ : MetricSpace PF
inst✝ : NormedAddTorsor F PF
f : PE ≃ᵢ PF
x y : PE
e : PE ≃ᵢ PE :=
  ((f.trans (pointReflection ℝ (midpoint ℝ (f x) (f y))).toIsometryEquiv).trans f.symm).trans
    (pointReflection ℝ (midpoint ℝ x y)).toIsometryEquiv
hx : e x = x
⊢ f (midpoint ℝ x y) = midpoint ℝ (f x) (f y)
state_after: E : Type u_1
PE : Type u_2
F : Type u_3
PF : Type u_4
inst✝⁷ : NormedAddCommGroup E
inst✝⁶ : NormedSpace ℝ E
inst✝⁵ : MetricSpace PE
inst✝⁴ : NormedAddTorsor E PE
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace ℝ F
inst✝¹ : MetricSpace PF
inst✝ : NormedAddTorsor F PF
f : PE ≃ᵢ PF
x y : PE
e : PE ≃ᵢ PE :=
  ((f.trans (pointReflection ℝ (midpoint ℝ (f x) (f y))).toIsometryEquiv).trans f.symm).trans
    (pointReflection ℝ (midpoint ℝ x y)).toIsometryEquiv
hx : e x = x
hy : e y = y
⊢ f (midpoint ℝ x y) = midpoint ℝ (f x) (f y)
tactic: have hy : e y = y := by simp [e]
state_before: E : Type u_1
PE : Type u_2
F : Type u_3
PF : Type u_4
inst✝⁷ : NormedAddCommGroup E
inst✝⁶ : NormedSpace ℝ E
inst✝⁵ : MetricSpace PE
inst✝⁴ : NormedAddTorsor E PE
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace ℝ F
inst✝¹ : MetricSpace PF
inst✝ : NormedAddTorsor F PF
f : PE ≃ᵢ PF
x y : PE
e : PE ≃ᵢ PE :=
  ((f.trans (pointReflection ℝ (midpoint ℝ (f x) (f y))).toIsometryEquiv).trans f.symm).trans
    (pointReflection ℝ (midpoint ℝ x y)).toIsometryEquiv
hx : e x = x
hy : e y = y
⊢ f (midpoint ℝ x y) = midpoint ℝ (f x) (f y)
state_after: E : Type u_1
PE : Type u_2
F : Type u_3
PF : Type u_4
inst✝⁷ : NormedAddCommGroup E
inst✝⁶ : NormedSpace ℝ E
inst✝⁵ : MetricSpace PE
inst✝⁴ : NormedAddTorsor E PE
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace ℝ F
inst✝¹ : MetricSpace PF
inst✝ : NormedAddTorsor F PF
f : PE ≃ᵢ PF
x y : PE
e : PE ≃ᵢ PE :=
  ((f.trans (pointReflection ℝ (midpoint ℝ (f x) (f y))).toIsometryEquiv).trans f.symm).trans
    (pointReflection ℝ (midpoint ℝ x y)).toIsometryEquiv
hx : e x = x
hy : e y = y
hm : e (midpoint ℝ x y) = midpoint ℝ x y
⊢ f (midpoint ℝ x y) = midpoint ℝ (f x) (f y)
tactic: have hm := e.midpoint_fixed hx hy
state_before: E : Type u_1
PE : Type u_2
F : Type u_3
PF : Type u_4
inst✝⁷ : NormedAddCommGroup E
inst✝⁶ : NormedSpace ℝ E
inst✝⁵ : MetricSpace PE
inst✝⁴ : NormedAddTorsor E PE
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace ℝ F
inst✝¹ : MetricSpace PF
inst✝ : NormedAddTorsor F PF
f : PE ≃ᵢ PF
x y : PE
e : PE ≃ᵢ PE :=
  ((f.trans (pointReflection ℝ (midpoint ℝ (f x) (f y))).toIsometryEquiv).trans f.symm).trans
    (pointReflection ℝ (midpoint ℝ x y)).toIsometryEquiv
hx : e x = x
hy : e y = y
hm : e (midpoint ℝ x y) = midpoint ℝ x y
⊢ f (midpoint ℝ x y) = midpoint ℝ (f x) (f y)
state_after: E : Type u_1
PE : Type u_2
F : Type u_3
PF : Type u_4
inst✝⁷ : NormedAddCommGroup E
inst✝⁶ : NormedSpace ℝ E
inst✝⁵ : MetricSpace PE
inst✝⁴ : NormedAddTorsor E PE
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace ℝ F
inst✝¹ : MetricSpace PF
inst✝ : NormedAddTorsor F PF
f : PE ≃ᵢ PF
x y : PE
e : PE ≃ᵢ PE :=
  ((f.trans (pointReflection ℝ (midpoint ℝ (f x) (f y))).toIsometryEquiv).trans f.symm).trans
    (pointReflection ℝ (midpoint ℝ x y)).toIsometryEquiv
hx : e x = x
hy : e y = y
hm :
  (pointReflection ℝ (midpoint ℝ x y)).toIsometryEquiv
      (f.symm ((pointReflection ℝ (midpoint ℝ (f x) (f y))).toIsometryEquiv (f (midpoint ℝ x y)))) =
    midpoint ℝ x y
⊢ f (midpoint ℝ x y) = midpoint ℝ (f x) (f y)
tactic: simp only [e, trans_apply] at hm
state_before: E : Type u_1
PE : Type u_2
F : Type u_3
PF : Type u_4
inst✝⁷ : NormedAddCommGroup E
inst✝⁶ : NormedSpace ℝ E
inst✝⁵ : MetricSpace PE
inst✝⁴ : NormedAddTorsor E PE
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace ℝ F
inst✝¹ : MetricSpace PF
inst✝ : NormedAddTorsor F PF
f : PE ≃ᵢ PF
x y : PE
e : PE ≃ᵢ PE :=
  ((f.trans (pointReflection ℝ (midpoint ℝ (f x) (f y))).toIsometryEquiv).trans f.symm).trans
    (pointReflection ℝ (midpoint ℝ x y)).toIsometryEquiv
hx : e x = x
hy : e y = y
hm :
  (pointReflection ℝ (midpoint ℝ x y)).toIsometryEquiv
      (f.symm ((pointReflection ℝ (midpoint ℝ (f x) (f y))).toIsometryEquiv (f (midpoint ℝ x y)))) =
    midpoint ℝ x y
⊢ f (midpoint ℝ x y) = midpoint ℝ (f x) (f y)
state_after: no goals
tactic: rwa [← eq_symm_apply, toIsometryEquiv_symm, pointReflection_symm, coe_toIsometryEquiv,
    coe_toIsometryEquiv, pointReflection_self, symm_apply_eq, @pointReflection_fixed_iff] at hm