An elementary proof of Ptolemy’s theorem
Man, Yiu-Kwong,Learning and Teaching Mathematics, 2019, 23-25 (2019),
publicationName = "Association for Mathematics Education of South Africa (AMESA)",
issn = "1990-6811",
abstract= "IntroductionPtolemy’s theorem is a well-known result in plane geometry and can be stated as follows:*If ABCD is a cyclic quadrilateral with sides a, b, c, d and diagonals e, f, then ac +bd = ef*In this article we present an elementary proof of Ptolemy’s theorem based on basic trigonometry, circle geometry and transformation geometry. The proof is different to those described elsewhere – see for example Johnson (1929), Coxeter & Greitzer (1967), Ostermann & Wanner (2012) and Miculita (2017)."
language="English",
type="Journal Article"