圆是几何图形中具有数学美的典型代表,它具有很多特殊的性质.例如:同弧或等弧所对的圆周角等于圆心角的一半,直径所对的圆周角是直角,直角所对的弦是直径,圆心到圆上各点的距离都相等……解决几何问题经常需要添加辅助线,这些辅助线往往成为解题的关键.常见辅助线有线段,射线,直线等.近年来出现了一些中考题,用常规方法求解难度很大,且过于繁琐.但如果根据题目特征添加一种特殊辅助线:辅助圆,就可以巧妙地运用圆的相关定理 A circle is a typical representative of mathematical beauty in geometry, and it has many special properties, for example, that the angle of the circle with respect to an arc or an arc equals half the angle of the circle, the angle of the circle with respect to the diameter is a right angle, Is the diameter, the distance from the center to the circle at each point are equal ... Solve the geometric problems often need to add auxiliary lines, these auxiliary lines are often the key to solving the problem.Common auxiliary lines are segments, rays, straight lines, etc. In recent years, some The examination questions, using conventional methods to solve difficult and too complicated, but if according to the topic features to add a special auxiliary line: auxiliary circle, you can skillfully use the circle of the relevant theorem