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Ptolemy's Inequality

Revision as of 12:16, 21 June 2006 by Puuhikki (talk | contribs) (A link where the proof can be found)

Ptolemy's inequality for a convex quadrilateral ABCD states that AB·CD + BC·DA ≥ AC·BD with equality iff ABCD is a cyclic quadrilateral.

A proof of Ptolemy's inequality.

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