All open problems
Source labels openChecked July 26, 2026
Erdős Problem 189: Parallelogram
Seems to be open, as of January 2025.
Mathematical statement
Seems to be open, as of January 2025.
Statement source: Erdős Problems statement material
Statement terms: Source-specific
Source-specific terms. Therefore does not assert reuse rights beyond attributed display.
Statement artifacts, not proofs
These records expose exact Lean propositions and statement-only wrappers. Defining a proposition does not supply a proof of it. A placeholder-bearing target also contains no proof. Elaboration checks syntax and types; it does not certify that a formalization perfectly captures every nuance of the informal problem.
Pinned Lean formulation 1
erdos_189.variants.parallelogram
Complete statement target, proof intentionally absentLean 4
theorem erdos_189.variants.parallelogram : ¬ Erdos189For (fun a b c d ↦ line[ℝ, a, b] ∥ line[ℝ, c, d] ∧ line[ℝ, a, d] ∥ line[ℝ, b, c]) (fun a b c d ↦ dist a b * dist b c * (∡ a b c).sin) := by sorry- Statement source
- Formal Conjectures
- Lean version
- v4.27.0
- Placeholder
- Present; no proof artifact
- Source evidence
- Pinned source index
- Fidelity review
- Community formulation
References