题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060833-34293.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060833-79004.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060833-24338.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060833-86925.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060834-49676.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060834-88775.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060834-18018.png)
(1)求证:
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060834-48071.png)
(2)求证:
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060835-74012.png)
答案
解析
试题分析:(1)证明:
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060835-70699.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060835-19039.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060835-57020.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060836-16631.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060836-71003.png)
又
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060835-70699.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060836-50645.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060836-90118.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060836-67748.png)
(2)证明:依题意可知:
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060837-33184.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060837-94144.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060835-70699.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060836-50645.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060837-69509.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060837-72819.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060838-86855.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060838-38645.png)
在
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060838-25929.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060838-32613.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060838-42127.png)
点评:立体几何的证明计算还可用空间向量的方法解决,根据题目已知条件选择最合适的方法思路
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060830-25535.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060830-46246.png)
的大小为( )
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060830-18406.png)
A.300 | B.450 | C.600 | D.900 |
A.平行 | B.相交 | C.异面 | D.以上均有可能 |
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060821-38498.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060821-67104.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060821-88507.png)
A.若![]() ![]() ![]() |
B.若![]() ![]() ![]() |
C.若![]() ![]() ![]() |
D.若![]() ![]() ![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060815-81869.png)
A. 2
B.
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060816-27866.png)
C.
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060816-80900.png)
D.
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022060816-30970.png)
A.60° | B.90° | C.45° | D.30° |
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