我们知道 ,针对圆的特殊几何性质 ,可以用圆心到直线的距离与圆的半径的大小关系来判定直线和圆的位置关系 .实际上 ,结合椭圆和双曲线的第一定义 ,直线和椭圆、双曲线的位置关系的判定也有类似的结论 .引理 1　平面上 ,两点Ｆ1 、Ｆ2 在直线ｌ的同侧 ,点Ｆ′1 和点Ｆ1 关于直 We know that for the special geometric properties of a circle, we can use the relationship between the distance from the center of the circle to the radius of the circle to determine the positional relationship between the line and the circle. In fact, the first definition of the ellipse and hyperbola is combined with the straight line and the ellipse, The determination of the positional relationship of the hyperbola also has a similar conclusion. On the 1st plane of Lemma, the two points F1 and F2 are on the same side of the straight line l, and the points F’1 and F1 are straight.