题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105722-48505.jpg)
A.![]() | B.![]() | C.![]() | D.![]() |
答案
解析
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105723-49485.jpg)
依题意得
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105723-97116.png)
可取n1=(-1,2,1),同理可得平面C1DF的一个法向量为n2=(2,-1,1),故平面A1DE与平面C1DF所成二面角的余弦值为
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105723-46603.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105722-98256.png)
核心考点
试题【如图所示,ABCD-A1B1C1D1是棱长为6的正方体,E,F分别是棱AB,BC上的动点,且AE=BF.当A1,E,F,C1共面时,平面A1DE与平面C1DF所】;主要考察你对空间向量的基本概念等知识点的理解。[详细]
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105716-73500.jpg)
(1)证明:MF⊥BD;
(2)若二面角A-BF-D的平面角的余弦值为
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105716-43553.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105702-63668.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105702-80901.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105702-37390.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105702-23262.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105702-62236.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105702-14941.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105702-55672.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105703-24989.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105703-25512.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105703-14356.png)
(1)求证:
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105703-12496.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105703-41873.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105703-52740.png)
(2)求平面
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105703-52740.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105703-93886.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105704-98149.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105656-70526.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105657-30724.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105640-67750.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105640-62424.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105640-36226.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105640-96892.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105640-28882.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105640-26282.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105640-36226.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105640-86827.png)
①
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105640-25321.png)
②
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105641-73647.png)
③直线
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105641-43336.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105640-26282.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105641-85232.png)
④
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105105641-57217.png)
其中正确的结论是( )
A.①③ | B.②④ | C.①③④ | D.①②③④ |
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