题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035012-26469.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035013-11172.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035013-38433.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035013-97289.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035013-31689.png)
(Ⅰ)求证:
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035014-13991.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035014-52910.png)
(Ⅱ)求二面角
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035014-58436.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035014-72122.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035015-84524.png)
解析
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035015-36588.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035015-15671.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035015-52953.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035016-18160.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035016-47726.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035016-13842.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035016-88709.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035014-13991.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035014-52910.png)
(Ⅱ)如图,连结
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035017-77039.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035017-70158.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035017-60877.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035017-20281.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035018-61607.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035018-80876.jpg)
设平面
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035018-34736.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035018-46065.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035019-93669.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035019-21108.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035019-69344.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035019-74641.png)
而平面
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035020-87742.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035020-40564.png)
由
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035020-91111.png)
二面角
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035014-58436.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106035020-88914.png)
【考点定位】本题结合熟知的等腰梯形这一底面考查了空间线面垂直的判定方法,通过建立空间直角坐标系考查了向量法求二面角的方法,等腰梯形这一底面是建立空间坐标系的基础,解题时要善于发现垂直关系
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106034955-83445.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106034956-25752.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106034956-99726.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106034956-82342.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106034956-63327.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106034957-76351.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106034957-97182.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106034957-68107.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106034958-92612.jpg)
A.己知直线a,b![]() ![]() |
B.若直线a平行平面α内的无数条直线,则直线a//平面α; |
C.若直线a垂直直线b在平面a内的射影,则直线a⊥b |
D.若直线a, b. c两两成异面直线,则一定存在直线与a,b,c都相交 |
(I)求证:直线CE//平面ABF;
(II)如果FG⊥平面ABCD求二面B一EF一A的平面角的余弦值.
(Ⅲ)若直线AF与平面 ABCD所成角为
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106034936-39752.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106034936-26701.png)
(1)证明:PN⊥AM.
(2)当λ取何值时,直线PN与平面ABC所成的角θ最大?并求该角最大值的正切值.
(3)是否存在点P,使得平面 PMN与平面ABC所成的二面角为45°.若存在求出l的值,若不存在,说明理由.
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106034925-64647.jpg)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106034915-70912.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106034915-18503.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106034916-92621.png)
①
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106034916-77614.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106034916-87970.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106034917-74849.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106034917-83053.png)
可由上述条件可推出的结论有 ;
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