Squaring the circle
It stood for two thousand years because it was impossible. Constructible lengths are algebraic of a special kind, and Lindemann proved that π is not algebraic at all. The answer came from algebra and analysis, far from the geometry in which it was asked. Impossibility proofs close questions just as firmly as constructions do.
Evidence tier V3 is the import default for a result the curation records as settled in the published record. No formal proof or certificate is attached to this page yet.
Posed Antiquity, Greek geometers. Closed 1882, Ferdinand von Lindemann.
Sources
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