1 . 如图是数学家
用来证明一个平面截圆锥得到的截面是椭圆的模型(称为丹德林双球模型):在圆锥内放两个大小不同的小球,使得它们分别与圆锥侧面、截面相切,设图中球
和球
的半径分别为1和3,
,截面分别与球
和球
切于点
和
,则此椭圆的长轴长为___________ .
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2 . 古希腊数学家阿波罗尼斯的著作《圆锥曲线论》是古代世界光辉的科学成果,它将圆锥曲线的性质网罗殆尽,几乎使后人没有插足的余地,他证明过这样一个命题:平面内与两定点距离的比为常数
(
且
)的点的轨迹是圆,后人将之称为阿波罗尼斯圆,现有椭圆
,
、
为椭圆
长轴的端点,
、
为椭圆
短轴的端点,动点
满足
,
的面积的最大值为
,
的面积的最小值为
,则椭圆
的离心率为______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f0a532e15e232cb4b99a8d4d07c89575.png)
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