相交弦定理、切割线定理反映的是两组与圆有关的等积线段或比例线段 ,这是再介绍一组 ,供同行参考 .命题 :三角形外接圆上任一点到三角形各顶点的距离与到各顶点所对边的距离之积相等 .此命题试证如下 :设△ABC内接于⊙O ,P是⊙O上任一点 ,连结PA、PB、PC ,分别作PA′⊥BC ,PB The intersecting string theorem and the cutting line theorem reflect the two sets of circle-related equal product line segments or proportional line segments. This is a group introduced again for reference by peers. Proposition: The distance from each point on the triangle circumcircle to each vertex of the triangle The product of the distances between the edges of the vertices is equal. The proposition of this proposition is as follows: Let △ABC be connected to ⊙O, P is any point on ⊙O, link PA, PB, PC, respectively, PA’⊥BC, PB