圆,具有十分丰富的性质,我们在处理直线形问题时,有时可借助圆的性质,使问题获得简解、巧解.下面是添作辅助圆的几种常见方法:11利用圆的定义添补辅助圆;21作三角形的外接圆;31运用四点共圆的判定方法:(1)若一个四边形的一组对角互补,则它的四个顶点共圆.(2)同底同侧张等角的三 Circles are very rich in nature. When we deal with linear problems, we can sometimes use the nature of circles to make the problem simple and clever. Here are a few common ways to use it as an auxiliary circle: 11 Make use of the definition of circles. Auxiliary circle; 21 as a circumcircle of a triangle; 31 Judgment method using four-point co-circle: (1) If a set of diagonals of a quadrilateral is complementary, its four vertices are co-circular. (2) Identical to the same side Isometric three