天天4050
幼苗
共回答了19个问题采纳率:94.7% 举报
(1)
![](https://img.yulucn.com/upload/7/af/7af9c956aca4dec73305be8470ebddea_thumb.jpg)
;(2)
![](https://img.yulucn.com/upload/0/99/099ce706886b9504827a9ba688192e4a_thumb.jpg)
.
(1)由椭圆过已知点和椭圆离心率可以列出方程组,解方程组即可,也可以分步求解;(2)直线方程和椭圆方程组成方程组,可以求解,也可以利用根与系数关系;然后利用中点坐标公式求解.
(1)将点(0,4)代入
![](https://img.yulucn.com/upload/e/7a/e7a810ab8a91837e238704828159eee9_thumb.jpg)
的方程得
![](https://img.yulucn.com/upload/1/63/163a740055a1ed0a5c8b077c06865f42_thumb.jpg)
,∴b=4,
又
![](https://img.yulucn.com/upload/b/7f/b7fbecf0118dfd0beb1a610a383c14e4_thumb.jpg)
得
![](https://img.yulucn.com/upload/f/b4/fb4a0716952ce24526c3ee9b5329492e_thumb.jpg)
,即
![](https://img.yulucn.com/upload/1/85/185422131d2fc5c7ca6edff2cc275dea_thumb.jpg)
, ∴
![](https://img.yulucn.com/upload/6/2b/62b5d3dd2ce630effd10b0e743ba2cb4_thumb.jpg)
,∴
![](https://img.yulucn.com/upload/e/7a/e7a810ab8a91837e238704828159eee9_thumb.jpg)
的方程为
(2)过点
![](https://img.yulucn.com/upload/f/be/fbe1426b28c85ed1cfe93bad2c2b0025_thumb.jpg)
且斜率为
![](https://img.yulucn.com/upload/c/ae/cae7fbc0198a7ff9905556a5da0fc6c8_thumb.jpg)
的直线方程为
![](https://img.yulucn.com/upload/3/2f/32f26991367e6d3592d6f13614bbbb9f_thumb.jpg)
,
设直线与C的交点为A
![](https://img.yulucn.com/upload/6/cd/6cd5c4c9fedbb6613992e7be44c2780d_thumb.jpg)
,B
![](https://img.yulucn.com/upload/6/d6/6d633ed6cdd13a3147f30b03122ae0c2_thumb.jpg)
,将直线方程
![](https://img.yulucn.com/upload/3/2f/32f26991367e6d3592d6f13614bbbb9f_thumb.jpg)
代入C的方程,得
![](https://img.yulucn.com/upload/b/6c/b6cefe18dbd750a66a944381c7896e5f_thumb.jpg)
,即
![](https://img.yulucn.com/upload/b/71/b71290324d2eb383cd0a5fc9b0587657_thumb.jpg)
,解得
![](https://img.yulucn.com/upload/7/c3/7c39ddfd8708fe740e4d2af23473550d_thumb.jpg)
,
![](https://img.yulucn.com/upload/1/af/1afdfef0f7c1ae413a01e9879a31b8fe_thumb.jpg)
,
![](https://img.yulucn.com/upload/a/49/a49ba5bb6e372ebfa9122220e4b0e8d8_thumb.jpg)
AB的中点坐标
![](https://img.yulucn.com/upload/b/ce/bcef2e529c68f71ba55d58fc33a144b7_thumb.jpg)
,
![](https://img.yulucn.com/upload/1/6d/16d3a2a6ef46f9a333ce438d7d9056ba_thumb.jpg)
,
即所截线段的中点坐标为
![](https://img.yulucn.com/upload/0/99/099ce706886b9504827a9ba688192e4a_thumb.jpg)
.
1年前
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