在平面几何中我们学习了圆的知识,解析几何中又进一步学习了圆的方程及有关知识。可以说,对于圆我们是比较熟悉的。学习椭圆时,椭圆的方程及有关的一些命题的计算与推证,和圆比较起来,就复杂了。但是,虽然椭圆与圆有很大的不同,但两者之间确有许多相似之处。实际上可以把圆看作是椭圆的一种特殊情况。圆的某些结论如果相应地推广到椭圆中去仍然成立,这就是“一般性寓于特殊性之中”。反过 In plane geometry, we learned the knowledge of the circle. In the analytic geometry, we further studied the circular equations and related knowledge. It can be said that we are more familiar with the circle. When learning an ellipse, the equations of the ellipse and the calculations and derivations of the relevant propositions are more complex than the circle. However, although ellipses and circles are very different, there are indeed many similarities between the two. In fact, the circle can be regarded as a special case of an ellipse. Some of the conclusions of the circle are still valid if they are extended into the ellipse accordingly. This is “generality in particularity.” Reverse