已知
,
,
是抛物线C:
上的一点,则
周长的最小值为____________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ab47bf43b2c5d6395129b80ddfbb1b24.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08ef03f452410ab19c6246567c427178.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c3577bf250e9110428ff34f518fbd9f2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6a11cb104b04c4e6a1be700e81da279a.png)
更新时间:2024-02-11 18:36:31
|
【知识点】 抛物线上的点到定点和焦点距离的和、差最值
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填空题-双空题
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较易
(0.85)
解题方法
【推荐1】探照灯、汽车灯等很多灯具的反光镜是抛物面(其纵断面是拋物线的一部分),正是利用了抛物线的光学性质:由其焦点射出的光线经抛物线反射之后沿对称轴方向射出.根据光路可逆图,在平面直角坐标系中,抛物线
,一条光线经过
,与
轴平行射到抛物线
上,经过两次反射后经过
射出,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/14bd426e7e1e65d91394da0b28d49f65.png)
________ ,光线从点
到
经过的总路程为________ .
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/5/853c5b83-fc2b-492e-873b-9c7170867603.png?resizew=100)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7c1ba86ffc6e5542b62319848c14acaa.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1a11db9cfc93cd1134b388ff5fbeea0d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b0145ad62ecc8ae00569ef2bd4ac5ea.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/14bd426e7e1e65d91394da0b28d49f65.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54a5d7d3b6b63fe5c24c3907b7a8eaa3.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/5/853c5b83-fc2b-492e-873b-9c7170867603.png?resizew=100)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/5/c7f6d403-b1a2-4dc9-af2e-5c3ddc166f66.png?resizew=193)
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填空题-单空题
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较易
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解题方法
【推荐2】已知抛物线
:
的焦点为
,点
在
上,若点
,则
的最小值为______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0261104a7c308433a0c0508ff20ea29a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/98b2cc0d2f6d3eee9a33db83e0c0830d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/508734095955bb96d52f37be4e681700.png)
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