近期在讲授普通高中课程标准实验教科书数学选修4-4《坐标系与参数方程》(人教A版)时,由第38页的例4引发了一系列的探究,得到了一些重要的结论,这些结论可以看成是圆的相交弦定理、切割线定理和切线长定理在圆锥曲线 In the recent lecture on mathematics elective 4-4 “Coordinate Systems and Parametric Equations” (Education A version) of ordinary high school curriculum standard experiment textbooks, a series of inquiries was triggered by Example 4 on page 38, and some important conclusions were obtained. These conclusions can be seen as intersecting string theorem, cutting line theorem and tangent length theorem in conic