笔者曾就几何光学的坐标解题法进行了探讨,对透镜成像和透镜组成像的坐标解题法分别刊登在“物理通报”86年6期和“物理教师”87年1期,本文拟探讨另一种更为简便的透镜成像解题方法,可称“平面几何解题法”。一、一道平面几何题如图1,AB、CD 均垂直于 DB。AD 和 CB 相交于 M,MN⊥DB ,求证:1/(AB)+1/(CD)=1/(MN)简单证明:MN∥AB.△DMN∽△DAB, The author once discussed the method of solving coordinate problems of geometric optics. The method of solving the problems of lens imaging and lens composition was respectively published in the “Physical Bulletin” of the 86th and the “Physics Teachers” of the 87th and 1st Periods. This article proposes to explore another simpler lens imaging problem solving method, which can be called “planar geometry solving method”. A plane geometry problem is shown in Figure 1. Both AB and CD are perpendicular to DB. AD and CB intersect at M, MN ⊥ DB. Proof: 1/(AB)+1/(CD)=1/(MN) Simple proof: MN ∥AB. △DMN ∽ △DAB,