kfwin2
幼苗
共回答了15个问题采纳率:100% 举报
已知椭圆
![](https://img.yulucn.com/upload/5/c4/5c477ab0ed67c4ded62c792feb4f40f8_thumb.jpg)
(
![](https://img.yulucn.com/upload/8/d9/8d94c929d63f28121a3f8b4d299e748a_thumb.jpg)
)的一个焦点坐标为
![](https://img.yulucn.com/upload/f/c6/fc6b7f8092c8f8335744d0baa78b0f2f_thumb.jpg)
,且长轴长是短轴长的
![](https://img.yulucn.com/upload/a/9b/a9b0d80547a31597c82ea70c1db2bd83_thumb.jpg)
倍.
(1)求椭圆
![](https://img.yulucn.com/upload/2/d5/2d51ee1bd7fc15b19f1571c42751ef2e_thumb.jpg)
的方程;
(2)设
![](https://img.yulucn.com/upload/9/0e/90e4b2dabc7074e1319abd42004f7a84_thumb.jpg)
为坐标原点,椭圆
![](https://img.yulucn.com/upload/2/d5/2d51ee1bd7fc15b19f1571c42751ef2e_thumb.jpg)
与直线
![](https://img.yulucn.com/upload/5/85/585a0481675f1c859361e566954884e6_thumb.jpg)
相交于两个不同的点
![](https://img.yulucn.com/upload/1/29/1295e1857020b76d45b3fc7d0aab08e5_thumb.jpg)
,线段
![](https://img.yulucn.com/upload/7/9e/79ed4500a8f136be799285db11a2e874_thumb.jpg)
的中点为
![](https://img.yulucn.com/upload/7/04/7043a5482d7cee3d2332ee5d7cb8c9e3_thumb.jpg)
,若直线
![](https://img.yulucn.com/upload/b/2b/b2b600dbe25f0ebaee7fcfeaf460b6c8_thumb.jpg)
的斜率为
![](https://img.yulucn.com/upload/f/8e/f8e140ec0bd9fe7f28ce2e2b22f6a38f_thumb.jpg)
,求△
![](https://img.yulucn.com/upload/7/c9/7c94946fb24f17b53839d031e49f22dd_thumb.jpg)
的面积.
(Ⅰ)题意得
![](https://img.yulucn.com/upload/1/eb/1eb4ce2f868734b4f925c3ad0b86bc60_thumb.jpg)
,
又
![](https://img.yulucn.com/upload/c/d1/cd1f69852c003eadbb5c1f1c566b308b_thumb.jpg)
,所以
![](https://img.yulucn.com/upload/4/7b/47b062904b53340c8bd8c484fbe6d260_thumb.jpg)
,
![](https://img.yulucn.com/upload/6/d3/6d30101727230a8906d4fd76e43d5381_thumb.jpg)
.
所以椭圆的方程为
![](https://img.yulucn.com/upload/6/a2/6a28245805f8789aa35b27ad56197313_thumb.jpg)
. ………………4分
(Ⅱ)设
![](https://img.yulucn.com/upload/9/79/979c264d3cd5a1a6db63422e30e4c6b9_thumb.jpg)
,
![](https://img.yulucn.com/upload/6/8d/68d36b71c2ed8e594d8e3c0c2d5db026_thumb.jpg)
,
![](https://img.yulucn.com/upload/1/79/17964bb241c3b297013b9197ddd0829f_thumb.jpg)
,
联立
![](https://img.yulucn.com/upload/4/c8/4c8d6b45719e49e6af4afccdef023d12_thumb.jpg)
消去
![](https://img.yulucn.com/upload/e/72/e7257438dc1dd169321ca21b9e037b3a_thumb.jpg)
得
![](https://img.yulucn.com/upload/b/34/b34a699f984d26c5d12bdb97d34745b8_thumb.jpg)
……(*), ………………6分
解得
![](https://img.yulucn.com/upload/0/b6/0b61d45b624d5ccc8a8b2c72beeb5e3f_thumb.jpg)
或
![](https://img.yulucn.com/upload/c/77/c77bf3b324460096ceb571e7cba9fd5f_thumb.jpg)
,所以
![](https://img.yulucn.com/upload/a/77/a776776791ac7df56fe4b34fc0616c89_thumb.jpg)
,
所以
![](https://img.yulucn.com/upload/c/b4/cb431e9237facd623654cd1e20f3672b_thumb.jpg)
,
![](https://img.yulucn.com/upload/8/9b/89bb4151f89fed19e19c6269cf5512ea_thumb.jpg)
, ………………8分
因为直线
![](https://img.yulucn.com/upload/b/2b/b2b600dbe25f0ebaee7fcfeaf460b6c8_thumb.jpg)
的斜率为
![](https://img.yulucn.com/upload/f/8e/f8e140ec0bd9fe7f28ce2e2b22f6a38f_thumb.jpg)
,所以
![](https://img.yulucn.com/upload/4/ea/4ea17bca66c77c15394cb70dcefd168d_thumb.jpg)
,
解得
![](https://img.yulucn.com/upload/c/a5/ca5bf35f84c1be07af542b917421b0d2_thumb.jpg)
(满足(*)式判别式大于零). ………………10分
![](https://img.yulucn.com/upload/9/0e/90e4b2dabc7074e1319abd42004f7a84_thumb.jpg)
到直线
![](https://img.yulucn.com/upload/2/67/2672c035e05ac9290efce5f2e0f94498_thumb.jpg)
的距离为
![](https://img.yulucn.com/upload/d/4b/d4bf779005751949c0807e0d75bdab7b_thumb.jpg)
,
![](https://img.yulucn.com/upload/c/ec/cec253f53f79a342dc5b1c5385d01d41_thumb.jpg)
,
所以△
![](https://img.yulucn.com/upload/7/c9/7c94946fb24f17b53839d031e49f22dd_thumb.jpg)
的面积为
略
1年前
1