同学们在学习几何时,若能借助某些直线、射线(如角平分线、垂线)为对称轴构造对称图形,便会给解题带来极大方便,下面介绍这类几何题的思路及方法。一、以角平分线为对称轴构造图形图1例1已知,如图1,在△ABC中,∠BAC=90°,AB=AC,BE平分∠ABC,CE⊥BE,求证:CE=21BD.分析:因为角是 When students learn geometry, if they can use some lines and rays (such as the angle bisector and the vertical line) to construct a symmetrical figure for the axis of symmetry, they will bring great convenience to solving problems. The following are the ideas of this kind of geometry problem. And methods. First, the angle bisector for the axis of symmetry structure Figure 1 Example 1 is known, as shown in Figure 1, in △ ABC, ∠BAC = 90 °, AB = AC, BE bisection ∠ ABC, CE ⊥ BE, verification: CE = 21BD. Analysis: Because the corner is