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PolygonalArcTerminalEndpointDiskCappedTaperSideLabelling

Proved
PolygonalArcTerminalEndpointDiskCappedTaperSideLabelling

by xuanji · Sep 28, 2026 · Mathlib 0df444a (Lean v4.33.1)

For every polygonal-arc segment, the terminal endpoint disk-capped taper chart labels the oriented tube sides in the reversed orientation: the oriented left half lies in the model right region and the oriented right half lies in the model left region, together with the transported topology and endpoint properties.

Preamble
import Definitions.Def_PlanarRot90
import Definitions.Def_PolygonalArcCollarCompatibleOrientedTubeData

open Set
open Classical
noncomputable section

set_option maxHeartbeats 900000
Formal statement
lemma PolygonalArcTerminalEndpointDiskCappedTaperSideLabelling
    (γ : PolygonalArc) {η : ℝ}
    (controlRadii : PolygonalArcCollarControlRadii γ η)
    (middleSegments : PolygonalArcCollarMiddleSegmentData γ controlRadii)
    (forbiddenMargins :
      PolygonalArcCollarMiddleForbiddenMargins γ controlRadii middleSegments)
    (compatibleTubes :
      PolygonalArcCollarCompatibleOrientedTubeData γ controlRadii middleSegments
        forbiddenMargins)
    (j : ℕ) (hj : j + 1 < γ.vertices.length) :
    let sep := compatibleTubes.orientedTubes.toPolygonalArcCollarSeparatedTubeData
    let d : EuclideanSpace ℝ (Fin 2) := γ.vertices[j] - γ.vertices[j + 1]
    let K : ℝ := compatibleTubes.terminalConeBound j hj
    let chart : EuclideanSpace ℝ (Fin 2) → EuclideanSpace ℝ (Fin 2) :=
      fun z => γ.vertices[j + 1] + z 0 • d + z 1 • PlanarRot90 d
    let a : ℝ :=
      controlRadii.radius ⟨j + 1, hj⟩ /
        dist γ.vertices[j + 1] γ.vertices[j]
    let C : Set (EuclideanSpace ℝ (Fin 2)) :=
      {z | 0 < z 0 ∧ z 0 ^ 2 + z 1 ^ 2 < a ^ 2 ∧ -K * z 0 < z 1 ∧
        z 1 < K * z 0}
    let L : Set (EuclideanSpace ℝ (Fin 2)) :=
      {z | 0 < z 0 ∧ z 0 ^ 2 + z 1 ^ 2 < a ^ 2 ∧ 0 < z 1 ∧
        z 1 < K * z 0}
    let R : Set (EuclideanSpace ℝ (Fin 2)) :=
      {z | 0 < z 0 ∧ z 0 ^ 2 + z 1 ^ 2 < a ^ 2 ∧ -K * z 0 < z 1 ∧
        z 1 < 0}
    let G : Set (EuclideanSpace ℝ (Fin 2)) :=
      {z | 0 < z 0 ∧ z 0 < a ∧ z 1 = 0}
    0 < a ∧
      IsOpen C ∧ IsOpen L ∧ IsOpen R ∧
      IsConnected L ∧ IsConnected R ∧
      IsConnected (chart '' L) ∧ IsConnected (chart '' R) ∧
      Disjoint L R ∧ Disjoint (chart '' L) (chart '' R) ∧
      (0 : EuclideanSpace ℝ (Fin 2)) ∉ C ∧ G ⊆ C ∧ C \ G = L ∪ R ∧
      (∀ z : EuclideanSpace ℝ (Fin 2),
        z 0 ^ 2 + z 1 ^ 2 < a ^ 2 →
          chart z ∈
            Metric.ball γ.vertices[j + 1] (controlRadii.radius ⟨j + 1, hj⟩)) ∧
      chart '' C ⊆
        Metric.ball γ.vertices[j + 1] (controlRadii.radius ⟨j + 1, hj⟩) ∧
      γ.vertices[j + 1] ∉ chart '' C ∧
      (∀ {t : ℝ}, 0 < t →
        chart (WithLp.toLp 2 (fun i : Fin 2 => if i = 0 then t else 0)) ≠
          γ.vertices[j + 1]) ∧
      ((AffineMap.lineMap γ.vertices[j] γ.vertices[j + 1]) ''
          Set.Ioo
            (1 - controlRadii.radius ⟨j + 1, hj⟩ /
              dist γ.vertices[j] γ.vertices[j + 1]) (1 : ℝ) ⊆
        chart '' G) ∧
      chart '' C \ chart '' G = chart '' L ∪ chart '' R ∧
      sep.leftHalf j hj ∩ chart '' C ⊆ chart '' R ∧
      sep.rightHalf j hj ∩ chart '' C ⊆ chart '' L := by sorry
Source
https://github.com/wpegden/crossing-consequences/blob/8769d142033fce042f502bf2857afb6b1375b5c3/Tablet/PolygonalArcTerminalEndpointDiskCappedTaperSideLabelling.lean#L1-242

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