托勒密定理在平面几何特别是圆的几何学中的应用非常广泛,如果将其引入到高中数学的教学中,不仅可以使学生开阔视野,而且还可使某些问题的解决非常的独到.本文将简单介绍其证法及其在高中数学教学中的应用.一、简述托勒密定理及其证明托勒密定理:圆内接四边形ABCD,则AB·CD+AD·BC=AC·BD证明:如图1在BD上取点P,使∠PAB=∠CAD,则ΔABP∽ΔACD于是AB=BP,即AB·CD=AC Ptolemy theorem is widely used in plane geometry, especially in circle geometry. If introduced into high school mathematics teaching, Ptolemy theorem not only broaden students’ horizons, but also make some problems unique. This article will briefly introduce its evidence method and its application in high school mathematics teaching.A brief description of the Ptolemy theorem and its proof Ptolemy’s theorem: ABCD, then AB · CD + AD · BC = AC · BD Proof: As shown in Figure 1, take a point P on the BD, so that ∠PAB = ∠CAD, ΔABP∽ΔACD then AB = BP, AB · CD = AC