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1 . 根据抛物线的光学性质可知,从抛物线的焦点发出的光线经该抛物线反射后与对称轴平行.沿直线
发出的光线经抛物线
反射后,与
轴相交于点
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/df5be1440d099f464ef46dee39de6010.png)
___________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/eefa44964db83759aff6fc8dd7ef8f28.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7089148c36cb3c39af71de653756396a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/241ce9bd28046ce9b90f43b391132884.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/df5be1440d099f464ef46dee39de6010.png)
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2 . 如图是抛物线形拱桥,当水面在
时,拱顶离水面
,水面宽
.当水位上升
后,水面宽是( )
![](https://img.xkw.com/dksih/QBM/2021/4/27/2709100149080064/2798309278277632/STEM/971ba94137774815a9fe106111e3687e.png?resizew=255)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f85fca60a11e1af2bf50138d0e3fe62.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f71a41641aa0d0e45a3c03d3d2c1196b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1e7854968bbf6576a1fd9926ee0d4d63.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/78a73babc7157e66044b22633f1a3609.png)
![](https://img.xkw.com/dksih/QBM/2021/4/27/2709100149080064/2798309278277632/STEM/971ba94137774815a9fe106111e3687e.png?resizew=255)
A.![]() | B.![]() | C.![]() | D.![]() |
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3 . 抛物线
上不同三点的纵坐标的平方成等差数列,则这三点( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3764ba3aa0a241787f4661026bb14053.png)
A.到原点的距离成等差数列 | B.到x轴的距离成等差数列 |
C.到y轴的距离成等差数列 | D.到焦点的距离的平方成等差数列 |
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