Difference between revisions of "Ptolemy's Inequality"
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| − | Ptolemy's Inequality for a | + | Ptolemy's Inequality for a [[quadrilateral]] ABCD states that AB·CD + BC·DA ≥ AC·BD with [[equal]]ity [[iff]] ABCD is a [[cyclic quadrilateral]]. |
[http://planetmath.org/encyclopedia/ProofOfPtolemysInequality.html A proof of Ptolemy's inequality.] | [http://planetmath.org/encyclopedia/ProofOfPtolemysInequality.html A proof of Ptolemy's inequality.] | ||
Revision as of 19:27, 24 June 2006
Ptolemy's Inequality for a quadrilateral ABCD states that AB·CD + BC·DA ≥ AC·BD with equality iff ABCD is a cyclic quadrilateral.
