本文将应用如下两条熟知的引理及相关的平面几何知识 ,推导出关于椭圆、双曲线、抛物线的切线性质的一组定理 .引理 1　椭圆 (或双曲线 )上任一点的切线与该点的两条焦半径成等角 .引理 2　抛物线上任一点的切线与该点的焦半径及其对称轴成等角 .定理 1　过椭圆 (或双曲线 )上 In this paper, we will use the following two well-known lemmas and related plane geometry knowledge to derive a set of theorems on the tangent properties of elliptic, hyperbolic, and parabolic. Lemma 1 The tangent to any point on an ellipse (or hyperbola) and this point The two radii of the focal radius are equiangular. Lemma 2 The tangent to any point on the parabola is equal to the focal radius of this point and its symmetry axis. Theorem 1 Over ellipse (or hyperbola)