文献[1]给出了如下的定义:在抛物线中,点D在抛物线对称轴上且与焦点同侧,直线l与对称轴垂直与焦点异侧,若点D与直线l到抛物线的顶点等距离,则称点D与直线l为“对偶元素”;在椭圆(双曲线)中,点D在长轴(实轴)所在的对称轴上,直线l与对称轴垂直且与曲线无交点,若点D与直线l在椭圆( [1] gives the following definition: In the parabola, the point D is on the same axis of the parabola and is the same as the focus, the line l is perpendicular to the axis of symmetry and the point of the focus is off, and if the point D and the vertex of the line l to the parabola In ellipse (hyperbola), the point D is on the axis of symmetry where the long axis (real axis) is located, the straight line l is perpendicular to the axis of symmetry and has no intersection with the curve, If the point D and the line l in the ellipse