题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130828-82829.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130828-57992.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130828-88189.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130828-77141.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130828-51830.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130828-75760.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130828-60987.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130828-82829.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130828-47302.jpg)
A.![]() | B.![]() | C.![]() | D.![]() |
答案
解析
试题分析:∵三棱锥
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130828-82829.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130829-81464.png)
又∵
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130828-75760.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130829-36239.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130829-80132.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130829-32384.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130830-54670.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130829-32384.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130830-56617.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130830-17699.png)
故选C.
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130822-23189.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130822-35756.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130822-23189.png)
A.![]() | B.![]() | C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130802-36724.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130803-52274.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130803-65872.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130803-79892.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130803-52803.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130804-57116.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130804-15554.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130804-65091.png)
(I)证明:
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130804-38498.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130805-78060.png)
(Ⅱ)若
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130805-78185.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130805-97063.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130805-16601.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130754-16210.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130754-58857.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130754-43409.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130754-63917.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130754-19107.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130755-64616.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130755-57009.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130755-32731.png)
(1)EF∥平面ACD;
(2)求证:平面
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130755-21687.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130755-49464.png)
(3)若平面
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130755-23108.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130755-49464.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130755-49846.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130755-12399.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130744-38911.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130744-49233.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130744-87400.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130744-53958.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130744-36610.png)
(1)求证:平面
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130744-20311.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130744-63625.png)
(2)当
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130745-24582.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130745-58550.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130744-87400.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021130745-59018.png)
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