Ptolemy's theorem

proper noun

A theorem that states in a cyclic quadrilateral, the product of the lengths of its diagonals is equal to the sum of the products of the lengths of the two pairs of opposite sides.

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Meanings

proper noun
  1. geometryA theorem that states in a cyclic quadrilateral, the product of the lengths of its diagonals is equal to the sum of the products of the lengths of the two pairs of opposite sides.

Origin

Named after the Greek astronomer and mathematician Ptolemy.

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Cite this entry
APA

Ptolemy's theorem. (n.d.). In WatkinsX Dictionary. Retrieved November 5, 2026, from https://dictionary.watkinsx.com/word/Ptolemy's%20theorem

MLA

“Ptolemy's theorem.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/Ptolemy's%20theorem. Accessed November 5, 2026.

Chicago

WatkinsX Dictionary, s.v. “Ptolemy's theorem,” accessed November 5, 2026, https://dictionary.watkinsx.com/word/Ptolemy's%20theorem.

Source: Ptolemy's theorem on Wiktionary, CC BY-SA 4.0.