题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002622-43158.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002623-41064.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002623-97060.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002623-86232.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002623-27280.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002624-12931.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002624-48587.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002624-43729.jpg)
(1)若过
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002624-54110.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002625-43765.png)
(2)在(1)的条件下,过右焦点
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002625-14697.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002625-33108.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002625-59474.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002625-29950.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002623-27280.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002626-31509.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002626-75883.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002626-38779.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002627-28879.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002627-86886.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002627-51557.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002627-66312.png)
解析
试题分析:(1)由题意
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002627-82464.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002628-89629.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002628-20427.png)
又
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002628-70279.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002628-41760.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002629-78433.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002629-46189.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002629-81061.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002629-33484.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002630-78679.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002630-24219.png)
又过
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002630-64548.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002630-75740.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002630-10451.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002631-81829.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002631-78671.png)
所求椭圆方程为
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002627-28879.png)
(2)有(1)知
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002631-49039.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002632-25559.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002632-32782.png)
将直线方程与椭圆方程联立
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002632-82805.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002632-30256.png)
设交点为
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002633-55891.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002633-42279.png)
则
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002633-50207.png)
若存在点
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002633-77401.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002634-18163.png)
由于菱形对角线垂直,所以
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002634-78986.png)
又
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002634-96280.png)
又
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002634-95050.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002635-30543.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002635-62593.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002635-77514.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002635-20173.png)
由已知条件知
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002636-73021.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002636-47794.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002636-51934.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002627-86886.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002627-51557.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002627-66312.png)
点评:难题,曲线关系问题,往往通过联立方程组,得到一元二次方程,运用韦达定理。本题求椭圆标准方程时,主要运用了椭圆的几何性质。对于存在性问题,往往先假设存在,利用已知条件加以探究,以明确计算的合理性。本题(III)通过确定m的表达式,利用函数思想,通过求函数的最值,确定得到其范围。
核心考点
试题【设椭圆的左、右焦点分别为,上顶点为,离心率为 , 在轴负半轴上有一点,且(1)若过三点的圆 恰好与直线相切,求椭圆C的方程;(2)在(1)的条件下,过右焦点作斜】;主要考察你对曲线与方程的应用等知识点的理解。[详细]
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002616-39291.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002616-80015.png)
A.![]() | B.![]() |
C.![]() | D.![]() |
A.焦点在x轴上的椭圆 | B.焦点在x轴上的双曲线 |
C.焦点在y轴上的椭圆 | D.焦点在y轴上的双曲线 |
![](http://img.shitiku.com.cn/uploads/allimg/20191026/20191026002601-75869.png)
A.![]() | B.![]() | C.![]() | D.![]() |
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