求角问题是《几何图形初步》这一章学习中的一个重点和难点.解答它们,要注意因题而异,巧妙“借力”.现举例如下:一、借转化之力这种“借力”是指找出图中要求的角与相关的角之间的和、差、倍、分关系.通过求出相关的角,从而求出要求的角.例1如图1,AB、CD都经过点O,OA平分∠COE,∠COE=100°,则∠BOD的度数为______.分析:由∠BOD+∠BOC=180°,得∠BOD=180°-∠BOC.要求 The problem of seeking angle is a key and difficult point in the chapter of “Preliminary Study of Geometry.” To answer them, we should pay attention to the differences between them, cleverly “leveraging.” Here are some examples: First, “Leverage ” refers to the relationship between the required angle and the relevant angle, the difference, the relationship between the times, by finding the relevant angle, thereby obtaining the required angle.Example 1 Figure 1 , AB, CD are through the point O, OA bisect ∠ COE, ∠ COE = 100 °, then ∠ BOD degrees ______. Analysis: ∠ BOD + ∠ BOC = 180 °, was ∠ BOD = 180 ° -∠BOC. Claim