圆是平面几何及平面解析几何研究的最基本、最重要的曲线 ,它具有许多优美、和谐的性质 ,本文借助直线的参数方程这个工具 ,探讨一类具有广泛性的圆的定值问题 ,其结论是如下的几个定理 .定理 1　设Ｐ是半径为Ｒ的圆Ｏ内任意一点 ,过点Ｐ任意引ｎ(ｎ≥ 2 )条直线ｌ1,ｌ2 ,… , The circle is the most basic and most important curve for plane geometry and plane analytic geometry research. It has many beautiful and harmonious properties. This article uses the parametric equation of the straight line tool to explore a class of universal circle constant value problems. The conclusion is the following several theorems. Theorem 1 Let P be any point within a circle O with a radius R, and point P any arbitrary n (n ≥ 2) lines l1, l2,...