1 . 图1是由正方形
组成的一个等腰梯形,其中
,将
、
分别沿
折起使得E与F重合,如图2.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/26/96241205-5ee2-45fe-a504-beb19971deba.png?resizew=315)
(1)设平面
平面
,证明:
;
(2)若二面角
的余弦值为
,求
长.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/69f0391c01548b0b5968f5b72cdd203a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fcd0ced286a0fbc7e4862f8147264277.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e742966e3711cfa53dce04022acf4bcc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5df7626240940eb340420a605e95aeee.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b5c4cd264c97c1f261229925cc5a6761.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/26/96241205-5ee2-45fe-a504-beb19971deba.png?resizew=315)
(1)设平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5ca0832e094d5c05ec13c38ae556b3f9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/01c0566d4ccf791d639c7823398941d7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/56adc934c9ad3cb261c5cbdc346b9631.png)
(2)若二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/445b51117626fbd3373e32acc514c64b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dee14db57f0c762aad845cf5b4a243c0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68a83fdd2ba72a2dba0b6b10bb3e06b9.png)
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2021-04-16更新
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7卷引用:四川省泸县第四中学2022-2023学年高二上学期期末考试数学(理)试题