Theorem: eq_lineMap_of_dist_eq_mul_of_dist_eq_mul
File: Mathlib/Analysis/Convex/StrictConvexBetween.lean

Proof steps:
state_before: V : Type u_1
P : Type u_2
inst✝¹¹ : NormedAddCommGroup V
inst✝¹⁰ : NormedSpace ℝ V
inst✝⁹ : StrictConvexSpace ℝ V
E : Type u_3
F : Type u_4
PE : Type u_5
PF : Type u_6
inst✝⁸ : NormedAddCommGroup E
inst✝⁷ : NormedAddCommGroup F
inst✝⁶ : NormedSpace ℝ E
inst✝⁵ : NormedSpace ℝ F
inst✝⁴ : StrictConvexSpace ℝ E
inst✝³ : MetricSpace PE
inst✝² : MetricSpace PF
inst✝¹ : NormedAddTorsor E PE
inst✝ : NormedAddTorsor F PF
r : ℝ
f : PF → PE
x y z : PE
hxy : dist x y = r * dist x z
hyz : dist y z = (1 - r) * dist x z
⊢ y = (AffineMap.lineMap x z) r
state_after: V : Type u_1
P : Type u_2
inst✝¹¹ : NormedAddCommGroup V
inst✝¹⁰ : NormedSpace ℝ V
inst✝⁹ : StrictConvexSpace ℝ V
E : Type u_3
F : Type u_4
PE : Type u_5
PF : Type u_6
inst✝⁸ : NormedAddCommGroup E
inst✝⁷ : NormedAddCommGroup F
inst✝⁶ : NormedSpace ℝ E
inst✝⁵ : NormedSpace ℝ F
inst✝⁴ : StrictConvexSpace ℝ E
inst✝³ : MetricSpace PE
inst✝² : MetricSpace PF
inst✝¹ : NormedAddTorsor E PE
inst✝ : NormedAddTorsor F PF
r : ℝ
f : PF → PE
x y z : PE
hxy : dist x y = r * dist x z
hyz : dist y z = (1 - r) * dist x z
this : y -ᵥ x ∈ [0-[ℝ]z -ᵥ x]
⊢ y = (AffineMap.lineMap x z) r
tactic: have : y -ᵥ x ∈ [(0 : E) -[ℝ] z -ᵥ x] := by
    rw [mem_segment_iff_wbtw, ← dist_add_dist_eq_iff, dist_zero_left, dist_vsub_cancel_right,
      ← dist_eq_norm_vsub', ← dist_eq_norm_vsub', hxy, hyz, ← add_mul, add_sub_cancel,
      one_mul]
state_before: V : Type u_1
P : Type u_2
inst✝¹¹ : NormedAddCommGroup V
inst✝¹⁰ : NormedSpace ℝ V
inst✝⁹ : StrictConvexSpace ℝ V
E : Type u_3
F : Type u_4
PE : Type u_5
PF : Type u_6
inst✝⁸ : NormedAddCommGroup E
inst✝⁷ : NormedAddCommGroup F
inst✝⁶ : NormedSpace ℝ E
inst✝⁵ : NormedSpace ℝ F
inst✝⁴ : StrictConvexSpace ℝ E
inst✝³ : MetricSpace PE
inst✝² : MetricSpace PF
inst✝¹ : NormedAddTorsor E PE
inst✝ : NormedAddTorsor F PF
r : ℝ
f : PF → PE
x y z : PE
hxy : dist x y = r * dist x z
hyz : dist y z = (1 - r) * dist x z
this : y -ᵥ x ∈ [0-[ℝ]z -ᵥ x]
⊢ y = (AffineMap.lineMap x z) r
state_after: case inl
V : Type u_1
P : Type u_2
inst✝¹¹ : NormedAddCommGroup V
inst✝¹⁰ : NormedSpace ℝ V
inst✝⁹ : StrictConvexSpace ℝ V
E : Type u_3
F : Type u_4
PE : Type u_5
PF : Type u_6
inst✝⁸ : NormedAddCommGroup E
inst✝⁷ : NormedAddCommGroup F
inst✝⁶ : NormedSpace ℝ E
inst✝⁵ : NormedSpace ℝ F
inst✝⁴ : StrictConvexSpace ℝ E
inst✝³ : MetricSpace PE
inst✝² : MetricSpace PF
inst✝¹ : NormedAddTorsor E PE
inst✝ : NormedAddTorsor F PF
r : ℝ
f : PF → PE
x y : PE
hxy : dist x y = r * dist x x
hyz : dist y x = (1 - r) * dist x x
this : y -ᵥ x ∈ [0-[ℝ]x -ᵥ x]
⊢ y = (AffineMap.lineMap x x) r

case inr
V : Type u_1
P : Type u_2
inst✝¹¹ : NormedAddCommGroup V
inst✝¹⁰ : NormedSpace ℝ V
inst✝⁹ : StrictConvexSpace ℝ V
E : Type u_3
F : Type u_4
PE : Type u_5
PF : Type u_6
inst✝⁸ : NormedAddCommGroup E
inst✝⁷ : NormedAddCommGroup F
inst✝⁶ : NormedSpace ℝ E
inst✝⁵ : NormedSpace ℝ F
inst✝⁴ : StrictConvexSpace ℝ E
inst✝³ : MetricSpace PE
inst✝² : MetricSpace PF
inst✝¹ : NormedAddTorsor E PE
inst✝ : NormedAddTorsor F PF
r : ℝ
f : PF → PE
x y z : PE
hxy : dist x y = r * dist x z
hyz : dist y z = (1 - r) * dist x z
this : y -ᵥ x ∈ [0-[ℝ]z -ᵥ x]
hne : x ≠ z
⊢ y = (AffineMap.lineMap x z) r
tactic: obtain rfl | hne := eq_or_ne x z