1 . 如图,在平面直角坐标系
中,已知二次函数
,直线l经过抛物线的顶点且与y轴垂直,垂足为Q.设抛物线上有一动点P从点
处出发沿抛物线向上运动,其纵坐标
随时间
的变化规律为
.现以线段
为直径作
.
![](https://img.xkw.com/dksih/QBM/2021/4/8/2695550622277632/2807507210428416/STEM/cd5a01ba-d030-4e92-92d3-fa79acbe96b1.png?resizew=275)
(1)点P在起始位置点B处时,试判断直线l与
的位置关系,并说明理由;在点P运动的过程中,直线l与
是否始终保持这种位置关系?请说明你的理由;
(2)若在点P开始运动的同时,直线l也向上平行移动,且垂足Q的纵坐标
随时间t的变化规律为
,则当t在什么范围内变化时,直线l与
相交?
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7ee31829d0d4d5f779a957d7df8058ab.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b46c1ab118b1278890bc60cf0b7f65e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/00183d9ff0c4204e3298029dc3e6033f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54015ff5b49e3283901da1291b6b921d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b05a62d60783712740c622a47e46ede7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/56d23f541360ec14437cf42bf4417efb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/abd13974aebe38eb2a1d744a01ea5aa5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/669e8dfb2b45e6f74d86408343a18fe2.png)
![](https://img.xkw.com/dksih/QBM/2021/4/8/2695550622277632/2807507210428416/STEM/cd5a01ba-d030-4e92-92d3-fa79acbe96b1.png?resizew=275)
(1)点P在起始位置点B处时,试判断直线l与
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/669e8dfb2b45e6f74d86408343a18fe2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/669e8dfb2b45e6f74d86408343a18fe2.png)
(2)若在点P开始运动的同时,直线l也向上平行移动,且垂足Q的纵坐标
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/46f6872ffb1934339c53c2c2282d5889.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e5c2f41ca54cc022633a8987029d5a4b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/669e8dfb2b45e6f74d86408343a18fe2.png)
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解题方法
2 . 已知椭圆
的中心为坐标原点
,焦点在
轴上,离心率为
,
分别为椭圆
的左、右焦点,点
在椭圆
上,以线段
为直径的圆经过点
,线段
与
轴交于点
,且
.
(1)求椭圆
的方程;
(2)设动直线
与椭圆
交于
两点,且
.求证:动直线
与
圆相切.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/860884c0017c8bceb5b0edff796c144f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5c38928a92bc4b44ed3c9b89769f5372.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/643ef7d761de0e794fc39937dc72ac6a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/da01a3abe1c9dc4e6283afa0dc1a0d39.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d053b14c8588eee2acbbe44fc37a6886.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/05f2188d99b44972f1e13d3a339ee5c7.png)
(1)求椭圆
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
(2)设动直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f85fca60a11e1af2bf50138d0e3fe62.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6670479a0083dd2dfd5ad55b47b1ab6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bc2abe13e2d4176f55f71677bbbb6eb4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f85fca60a11e1af2bf50138d0e3fe62.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2845cff59808d0945644a6c867e40740.png)
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