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1 . 如图,已知
为正三角形,D为AB的中点,E在AC上,且
,现沿DE将
折起,折起过程中点A仍然记作点A,使得平面
平面BCED,在折起后的图形中.
![](https://img.xkw.com/dksih/QBM/2021/9/13/2807128439554048/2815225309601792/STEM/80d94deb-2f09-4c04-872f-88daac4f7a21.png?resizew=472)
(1)在AC上是否存在点M,使得直线
平面ABD.若存在,求出点M的位置;若不存在,说明理由.
(2)求平面ABD与平面ACE所成锐二面角的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/eb8f6c9335373be2e09046a1e51424f8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a25c28359f8d8da9eaf4672a6cf8ae4f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4d28c625d7ac6878957facc8274d459c.png)
![](https://img.xkw.com/dksih/QBM/2021/9/13/2807128439554048/2815225309601792/STEM/80d94deb-2f09-4c04-872f-88daac4f7a21.png?resizew=472)
(1)在AC上是否存在点M,使得直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cb6dfed58659a9cab4d1836c3d2effdc.png)
(2)求平面ABD与平面ACE所成锐二面角的余弦值.
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2021-09-24更新
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2卷引用:福建省厦门第六中学2021-2022学年高二上学期开学适应性练习数学试题