折纸又称“工艺折纸”,是一种把纸张折成各种不同形状物品的艺术活动,在我国源远流长. 某些折纸活动蕴含丰富的数学内容,例如:用圆形纸片,按如下步骤折纸,可折出一个椭圆.
![](https://img.xkw.com/dksih/QBM/2021/1/28/2646018424455168/2648237748101120/STEM/8b52d5d840f142899dbde5e76bca0822.png?resizew=263)
![](https://img.xkw.com/dksih/QBM/2021/1/28/2646018424455168/2648237748101120/STEM/2b4845d0-1061-4c4f-81ac-6a9c09a074c9.png?resizew=323)
步骤1:设圆心是F,在圆内不是圆心处取一点,标记为E;
步骤2:把纸片对折,使圆周正好通过点E,此时圆周上与点E重合的点标记为G;
步骤3:把纸片展开,于是就留下一条折痕,此时GF与折痕交于点P;
步骤4:不断重复步骤2和3,能得到越来越多条的折痕和越来越多的交点P,所有交点P组成的图形便是一个椭圆.
现已知圆形纸片的半径为4,定点E到圆心F的距离为2,
为EF中点,所有交点P组成的椭圆记为
.
(1)以EF所在的直线为x 轴,以O为原点建立平面直角坐标系,求椭圆
的标准方程;
(2)设直线
与椭圆
交于A,
两点,且
,试问点
到直线
的距离是否为定值?如果是定值,则求该定值;如果不是定值,则说明理由.
![](https://img.xkw.com/dksih/QBM/2021/1/28/2646018424455168/2648237748101120/STEM/8b52d5d840f142899dbde5e76bca0822.png?resizew=263)
![](https://img.xkw.com/dksih/QBM/2021/1/28/2646018424455168/2648237748101120/STEM/2b4845d0-1061-4c4f-81ac-6a9c09a074c9.png?resizew=323)
步骤1:设圆心是F,在圆内不是圆心处取一点,标记为E;
步骤2:把纸片对折,使圆周正好通过点E,此时圆周上与点E重合的点标记为G;
步骤3:把纸片展开,于是就留下一条折痕,此时GF与折痕交于点P;
步骤4:不断重复步骤2和3,能得到越来越多条的折痕和越来越多的交点P,所有交点P组成的图形便是一个椭圆.
现已知圆形纸片的半径为4,定点E到圆心F的距离为2,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
(1)以EF所在的直线为x 轴,以O为原点建立平面直角坐标系,求椭圆
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
(2)设直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f85fca60a11e1af2bf50138d0e3fe62.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3825ccc273ef9a672a606432d165b866.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f85fca60a11e1af2bf50138d0e3fe62.png)
更新时间:2021-01-31 23:16:24
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【推荐1】已知椭圆
的左、右焦点分别是
,
,离心率为
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且垂直于x轴的直线被椭圆C截得的线段长为1.
(1)求椭圆C的方程;
(2)设点P在直线
上,过点P的两条直线分别交曲线C于A,B两点和M,N两点,且
,求直线AB的斜率与直线MN的斜率之和.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/851a5d6ec23256f9b4a9e98aa92945fe.png)
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(1)求椭圆C的方程;
(2)设点P在直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1e8ebd7c4463e7311f7ab4d7cd7d241.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fd2fa68cbadae8596b1f88a20994fb01.png)
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【推荐2】如图,在平面直角坐标系
中,已知
分别是椭圆
的左、右焦点,
分别是椭圆
的左、右顶点,
为线段
的中点,且
.
![](https://img.xkw.com/dksih/QBM/2016/2/26/1572503398604800/1572503404421120/STEM/4739a4ca982345a78cf4213471d899e8.png?resizew=193)
(1)求椭圆
的方程;
(2)若
为椭圆
上的动点(异于点
),连接
并延长交椭圆
于点
,连接
并分别延长交椭圆
于点
连接
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的斜率存在且分别为
.试问是否存在常数
,使得
恒成立?若存在,求出
的值;若不存在,说明理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7ee31829d0d4d5f779a957d7df8058ab.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4d2a97987f71835f519b462f5b8f5957.png)
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(1)求椭圆
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/01c74a907dda6bb7d9d56d009d9df253.png)
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【推荐1】已知椭圆
的焦距为2,点
在椭圆C上.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/10/16/5b03f7a5-7c48-41a1-8b43-dfd1c9c4bfe9.png?resizew=240)
(1)求椭圆C的方程;
(2)点P为椭圆C上异于顶点的任意一点,点M、N分别与点P关于原点、y轴对称.连接MN与x轴交于点E,并延长PE交椭圆C于点Q.试问:
是否为定值?若是,请求出该定值;若不是,请说明理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ad523e69a1bf925e73a22900b9855df2.png)
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(1)求椭圆C的方程;
(2)点P为椭圆C上异于顶点的任意一点,点M、N分别与点P关于原点、y轴对称.连接MN与x轴交于点E,并延长PE交椭圆C于点Q.试问:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ec8870e4bf111e3653f6aace28f20243.png)
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【推荐2】已知中心在原点的椭圆
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(2)过点
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