解与圆有关的几何问题时,常常需要添加适当的辅助线将复杂的图形转化为基本图形,从而方便求解.为帮助大家正确理解并掌握圆中有关计算或证明题的一般解法,现就圆中辅助线的常规作法分类例析如下.一、圆中有弦,常作弦心距,或者作垂直于弦的半径或直径,有时还要连结过弦端点的半径例1如图1,圆O的两条弦AB、CD互相垂直,垂足为E,且 When solving geometric problems related to circles, it is often necessary to add appropriate auxiliary lines to transform complex graphics into basic graphics so as to facilitate the solution. In order to help people understand and master the general solution to calculations or proofs in the circle, it is now Examples of conventional methods for classifying auxiliary lines are as follows. 1. There is a string in the circle, often as a string center distance, or as a radius or diameter perpendicular to the string, and sometimes the radius of the end of the string too. Example 1 The two strings AB and CD of O are perpendicular to each other, and the foot is E, and