如图,在长方体ABCD﹣A1B1C1D1中,AD=AA1=1,AB=2,点E在棱AB上移动.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/11/0f1e37e2-fe36-4475-aa28-53a1943a99a5.png?resizew=195)
(1)证明:D1E⊥A1D;
(2)若EB
,求二面角D1﹣EC﹣D的大小.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/11/0f1e37e2-fe36-4475-aa28-53a1943a99a5.png?resizew=195)
(1)证明:D1E⊥A1D;
(2)若EB
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7b8a8c23e2d89b7e124bc5ff2c20616f.png)
更新时间:2020-01-19 11:18:05
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【推荐1】已知空间三点A(0,2,3),B(-2,1,6),C(1,-1,5).
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【推荐2】已知空间三点A(0,2,3),B(-2,1,6),C(1,-1,5).
(1)若
,且
分别与
,
垂直,求向量
的坐标;
(2)若
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(1)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/da032e305b3ad38754e2d52b8ca086bb.png)
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(2)若
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【推荐1】如图,三角形
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,
,
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(2)求平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4734735213b599a9915e1ed91a5d8ce4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/62871bb0dff211fc3bd80f9066c25b29.png)
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【推荐2】如图,已知长方体ABCD-A1B1C1D1中,AB=3,BC=2,CC1=5,E是棱CC1上不同于端点的点,且
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/362510257920a569ff1c3bebc4e2e10a.png)
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【推荐3】如图所示,已知四棱柱
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为直角梯形,
,
,
,平面
平面
,
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![](https://img.xkw.com/dksih/QBM/2021/4/15/2700230680199168/2700531540860928/STEM/414e6afb-8aac-403e-91c1-311118841eee.png?resizew=276)
(1)若
为
的中点,
为线段
上的一动点,当
平面
,求
的长;
(2)在(1)的条件下,求二面角
的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e09725691ee7851f54c0dee86b2bf55.png)
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(1)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
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(2)在(1)的条件下,求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f6ccd3bb218ecb3dc1319d24dca57f81.png)
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