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10 changes: 8 additions & 2 deletions FormalConjectures/ErdosProblems/1071.lean
Original file line number Diff line number Diff line change
Expand Up @@ -49,8 +49,14 @@ theorem erdos_1071.parts.i :
(T : Set (ℝ² × ℝ²)).Pairwise SegmentsDisjoint) S := by
sorry

/-- Is there a region $R$ with a maximal set of disjoint unit line segments that is countably infinite? -/
@[category research open, AMS 52]
/-- Is there a region $R$ with a maximal set of disjoint unit line segments that is countably infinite?
Solved affirmatively by [Fo99], who gave an explicit construction.


This was formalized in Lean by Alexeev using Aristotle and ChatGPT.
-/
@[category research formally solved using lean4 at
"https://github.com/plby/lean-proofs/blob/main/src/v4.24.0/ErdosProblems/Erdos1071b.lean", AMS 52]
theorem erdos_1071.parts.ii :
answer(sorry) ↔ ∃ (R : Set ℝ²) (S : Set (ℝ² × ℝ²)),
S.Countable ∧ S.Infinite ∧
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