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Problem 97 and its pinned multiplicity formulation

Proved
Erdos9796Mission.problem97_iff_exists_pinnedMultiplicity_le_three

by mysticflounder · Sep 11, 2026 · Mathlib 0df444a (Lean v4.33.1)

discrete-geometryerdos-97pinned-distancesreformulation

Problem 97 implies that every nonempty finite planar point set in strictly convex position contains a point whose pinned distance multiplicity is at most three. The converse implication also holds. These two implications restate the open problem without proving it.

Preamble
import Definitions.Def_Erdos9796Mission_PinnedMultiplicity
Formal statement
theorem Erdos9796Mission.problem97_iff_exists_pinnedMultiplicity_le_three :
    Erdos9796Mission.Problem97 ↔
      ∀ A : Finset Erdos9796Mission.Plane,
        A.Nonempty → Erdos9796Mission.ConvexIndep (A : Set Erdos9796Mission.Plane) →
          ∃ p ∈ A, Erdos9796Mission.pinnedMultiplicity A p ≤ 3 := by sorry
Source
https://github.com/mysticflounder/erdos-97-96-formalization/blob/3d0e9306396f0aa6639f4453174693990fe9c242/lean/Erdos9796Proof/P97/PinnedMultiplicity.lean#L241-L262

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