1 . 已知椭圆
,点
在椭圆上,如图,用
表示椭圆在点
处切线的单位向量.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/12/30/198f7b15-d256-45b8-8ad4-3cc9057793bf.png?resizew=120)
(1)设
,求
的最大值;
(2)是否存在定圆
,使得圆
的任一切线与
的交点
满足
,若存在,求出圆
方程,若不存在,请说明理由
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d4a6e483672a226118dff5a39aa28449.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6f4fbb5a4568dd3e4baec9f8358552b4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/58e8744362c6e224146461b97faf9821.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/12/30/198f7b15-d256-45b8-8ad4-3cc9057793bf.png?resizew=120)
(1)设
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/75874285daf265905257368573ded035.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4fe7d5809da02c15a43a0e9a898b9086.png)
(2)是否存在定圆
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c0a21698cc2ceabd28d995692ab2bfc7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/01c74a907dda6bb7d9d56d009d9df253.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3825ccc273ef9a672a606432d165b866.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
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2 . 设点
,过点F作斜率为k的直线l交椭圆
于C,D两点.
(1)记直线
的斜率分别为
.从下列①②③三个式子中任选其一,当k变化时,判断该式子是否为定值,若是,求出定值;若不是,请说明理由.
①
;②
;③
.
(2)当直线
分别交双曲线
的下支于P,Q两点(异于点B)时,求
的取值范围.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/20421239f70724807fc2e42f74b1f02d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f182db8ffa0d36588407eae8aeb7aa92.png)
(1)记直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5913ac8f576f9389802005ae712205d0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3c65902e35640cf2c8d4111c36b40145.png)
①
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6b881044b5c73db6fcce110525741b02.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/89c20aa9e89d8cc15be390051124ee5d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0601dc0a83ff1c3b01dce7cdaa18cabb.png)
(2)当直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2013303974d530fce9a9930938f4c2b6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2aea802c49af59b44b8de07f6ef56d90.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411e6e928c39bb54f031aa3e5d492852.png)
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