1 . 如图,矩形
中,
,
,
在
边上,且
,将
沿
折到
的位置,使得平面
平面
.
(Ⅰ)求证:
;
(Ⅱ)求二面角
的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d2c15801fee2405573677484f5dcfa4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/09d27bd71d79cb19eb554175e4ef0867.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9e52a8f07834cbbbe4224962672fbbb2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/82773737609e65dea3c5c67099f1b10d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a25c28359f8d8da9eaf4672a6cf8ae4f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68a83fdd2ba72a2dba0b6b10bb3e06b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68696b781af2609327222d22cb7bab3f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b348d4333ecdfc3e3b1ba16dc312550d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/01ff27eea7545bb06f9472f91290c54e.png)
(Ⅰ)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4ced76e1ee551955a877688618b1f4ad.png)
(Ⅱ)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4d5a101bb92bd721e35acc7023154b44.png)
![](https://img.xkw.com/dksih/QBM/2017/4/18/1668561570709504/1668648730017792/STEM/cd7d6f1167504c9eb741ff615f56b857.png?resizew=149)
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2017-04-18更新
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2054次组卷
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5卷引用:内蒙古呼和浩特市金山学校2019-2020学年度高一下学期开学调研理科数学试题