在三角形、四边形这两章的学习中,我们经常会碰到线段的相等关系、和差关系、倍数关系的推理问题,但圆中涉及到线段倍数关系的题目并不多.本文通过对一道例题的分析,给出几种解题的策略,供同学们参考.例题如图1,点A、B、C、D在⊙O上,AC⊥BD于点E,过点O作OF⊥BC于点F.求证:(1AEB∽OFC;(2)AD=2FO.分析(1)要证AEB∽OFC就得围绕相似三角形的几种判别方法.AC⊥BD与OF⊥BC为我们提供了一组直角相等,下面就 In the study of triangle and quadrangle, we often encounter the equal relation of the line segments, and the reasoning of the relationship between the difference and the multiple, but there are not many problems in the circle concerning the relationship between the multiple of line segments. Of the problem, as shown in Figure 1, point A, B, C, D in ⊙ O, AC ⊥ BD in the point E, O point O for OF ⊥ BC Point F. Proof: (1AEB ∽ OFC; (2) AD = 2FO. Analysis (1) to prove  AEB ∽ OFC there are several similar methods to determine the triangle. AC ⊥ BD and OF ⊥ BC provides us with A set of right angles are equal, just below