题目内容
(本小题满分12分)已知椭圆
的左、右焦点分别为
、
,其中
也是抛物线
的焦点,
是
与
在第一象限的交点,且
.
(1)求椭圆
的方程;
(2)已知菱形
的顶点
在椭圆
上,顶点
在直线
上,求直线
的方程.
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134920850794.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134920865213.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134920881215.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134920881215.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134920912444.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134920928327.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134920943218.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134920959222.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134920975500.gif)
(1)求椭圆
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134920943218.gif)
(2)已知菱形
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921006301.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921021246.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134920943218.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921053253.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921084466.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921099234.gif)
(1)
(2)![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921131437.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921115491.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921131437.gif)
(1)设
.
由抛物线定义,
,
.
在
上,
,又![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921224311.gif)
或
舍去.
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921287449.gif)
∴椭圆
的方程为
.
(2)∵直线
的方程为
为菱形,
,设直线
的方程为![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921583397.gif)
、
在椭圆
上,
.
设
,则
.
.
的中点坐标为
,由
为菱形可知,点
在直线
上,
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921833755.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921864584.gif)
∴直线
的方程为
,即
.
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921146924.gif)
由抛物线定义,
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921162721.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921177503.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921177716.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921193216.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921209593.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921224311.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921240573.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921255380.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921271370.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921287449.gif)
∴椭圆
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921193216.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921115491.gif)
(2)∵直线
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921427249.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921536637.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921552439.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921567233.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921583397.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231349215991458.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921630200.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921193216.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921677710.gif)
设
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921723615.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921739520.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231349217551541.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921770242.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921786529.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921801397.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921786529.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921833579.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921833755.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921864584.gif)
∴直线
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921567233.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921895384.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134921131437.gif)
![](http://thumb.zyjl.cn/images/loading.gif)
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