在长方体ABCD-A1B1C1D1中,求证:
![](https://img.xkw.com/dksih/QBM/2019/3/26/2169052634587136/2171063875649536/STEM/923ee4b098c14fa6a8f665525ee24d9a.png?resizew=265)
(1)AB∥平面A1B1C;
(2)平面ABB1A1⊥平面A1BC.
![](https://img.xkw.com/dksih/QBM/2019/3/26/2169052634587136/2171063875649536/STEM/923ee4b098c14fa6a8f665525ee24d9a.png?resizew=265)
(1)AB∥平面A1B1C;
(2)平面ABB1A1⊥平面A1BC.
更新时间:2019-03-29 19:03:40
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解答题-证明题
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解题方法
【推荐1】如图,在正方体
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【推荐2】在三棱柱
中,
,
,点
是
的中点.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/14/09c530b3-cc95-4ad7-bca2-15d60f5dbfb0.png?resizew=204)
(1)求证:
平面
;
(2)若侧面
为菱形,求证:
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42d3a82b8e587ee890467835bc4e854c.png)
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(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4557a368725226f2c8ea2efb7d30e478.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cbc7e774e4ae40c23bf4ceed179230ca.png)
(2)若侧面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6ac61c24f99a4e466f1e2ea011893866.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a1515a445310d259a080d02e16c2e58e.png)
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【推荐1】如图,在三棱锥
中,
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![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/22/5d30685d-39d4-43d7-841d-f1cb6b99db3e.png?resizew=190)
(1)证明:平面
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![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/22/5d30685d-39d4-43d7-841d-f1cb6b99db3e.png?resizew=190)
(1)证明:平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/17580410bf63dba4fe164265afaac4cc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4c54d01623f09f23103f03ba1135fc6a.png)
(2)若
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5f1854ba6cc92481d7a616bd2788a47e.png)
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【推荐2】如图,在矩形
中,
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把△
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内的射影
恰好落在
上.
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(1)求证:平面
平面
;
(2)求二面角
的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
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(1)求证:平面
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/771e26b73c6b0386284e98f237a00ead.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/696ae55a4efddffcd268d19eb6394f66.png)
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