三种圆锥曲线(椭圆、抛物线、双曲线)性质不一,各显其妙.但它们源出一族,性质间有许多相通之处,特别是一些共同的性质,其优美简洁之处,令人叫绝.本文撷取一二,共飨之.性质1如图1,已知点P是圆锥曲线C上一点,过焦点F作焦半径PF的垂线交相应准线l于点Q,则直线PQ为曲线C的切线,切点 The three kinds of conic curves (ellipses, parabolas, hyperbolic curves) are different in nature, each showing its own wonderfulness, but they come from different families and have many similarities in their properties. In particular, they have some common features, As shown in Figure 1. Properties 1 As shown in Figure 1, the known point P is the conical curve C, the focal point F for the focal radius PF vertical line corresponding to the line l at point Q, then the straight line PQ is the tangent of the curve C, tangent point