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解题方法
1 . 双曲线的光学性质如下:如图1,从双曲线右焦点
发出的光线经双曲线镜面反射,反射光线的反向延长线经过左焦点
.我国首先研制成功的“双曲线新闻灯”,就是利用了双曲线的这个光学性质.某“双曲线灯”的轴截面是双曲线一部分,如图2,其方程为
分别为其左、右焦点,若从右焦点
发出的光线经双曲线上的点
和点
反射后(
在同一直线上),满足
.
(1)当
时,求双曲线的标准方程;
(2)过
且斜率为2的直线与双曲线的两条渐近线交于
两点,点
是线段
的中点,试探究
是否为定值,若不是定值,说明理由,若是定值,求出定值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a3fb78c5f885034612c0e030b920143d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f5076289823db419f94e9c0c8f4aafd9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1a6f05de8a75650b53e2238ed8efaf8a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a3fb78c5f885034612c0e030b920143d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8994a55ea8ef036dd1d3504c9830ff56.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4225b4f584708b614453fb5876f6a4f7.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/6/4/58286785-5710-457d-9730-260ad57675f6.png?resizew=380)
(1)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/57dfc9d1109fe41145cc892b5702d9fb.png)
(2)过
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a3fb78c5f885034612c0e030b920143d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2fe7fd9b0c3c203a053a7ea52b71e7c9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/09fcb20a6972108871adbf284f9e5006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/df68611c0b08d2a333672c7743f362c0.png)
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