如图所示,在正三棱柱ABC-A1B1C1中,已知D,E分别为BC,B1C1的中点,点F在棱CC1上,且EF⊥C1D.求证:
(1)直线A1E∥平面ADC1;
(2)直线EF⊥平面ADC1.
(1)直线A1E∥平面ADC1;
(2)直线EF⊥平面ADC1.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/19/c7f37319-cba0-411c-a849-f97de2e70e19.png?resizew=170)
更新时间:2019-04-23 18:47:46
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【推荐1】已知四边形
为直角梯形,
,
为等腰直角三角形,平面
平面
为
的中点,
.
平面
;
(2)求
与平面
所成角的正弦值.
(3)求二面角
的正弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4795ee1f96b430529934e2231b38885d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dcdb57d8e4041a23abe672105716e587.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/93edc7bb513f40a89173121c8570cd65.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/23d11e19c84255eb0431415c2dec553d.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c372d059202ec388960b125d4a87dc84.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/218054144a13435580cd132b9459546c.png)
(2)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8f571a1aac46c6d0cf440c0ec2846bf9.png)
(3)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/816b7f285cc55bbe5bf873538ba87230.png)
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【推荐2】如图,在四棱锥
中,底面ABCD为等腰梯形,
,
,E为AP的中点.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/8/24/ea8f4798-8e8d-4286-9de4-f01aa876143c.png?resizew=157)
(1)证明:
平面PBC.
(2)求四棱锥
外接球的表面积.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0585b6c0f156eecf9662b9846d4eb693.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5f79863ffcfa63117ca6741b20a48e69.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a05ef25a6b40700f28f81782b1c3b9d2.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/8/24/ea8f4798-8e8d-4286-9de4-f01aa876143c.png?resizew=157)
(1)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/063510e3c1fb6a7ccc3b8e3e3c7d660e.png)
(2)求四棱锥
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/80c753cb1eb73fd8d136d00462970797.png)
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【推荐1】如图,在三棱台
中,
,
平面
,平面
平面
.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/5/3/45be9cee-f747-4ad5-a024-fa8e3661b7e5.png?resizew=112)
(1)求证:
;
(2)若
,
的面积为4,求二面角
的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42d3a82b8e587ee890467835bc4e854c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60a9e3a0abf0df191f89169468f95bbe.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5845ccc0d735dc14c92a8926d9b1def6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1e3a59d7bf91a7540e35ce0011ad9b97.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ab3e0dba5705e1d749cfb21ebbb2ed93.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/5/3/45be9cee-f747-4ad5-a024-fa8e3661b7e5.png?resizew=112)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b1de5964353beb55c5058b2a431eecaf.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c2a61472439de1ba85cfe33840b775f2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c510b85dfbca0e3ab0744655d77e8c93.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ee3eb81e99c84589a3387d6ba0e6305a.png)
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解题方法
【推荐2】如图①,直角梯形
中,
,
,点
,
分别在
,
上,
,
,将四边形
沿
折起,使得点
,
分别到达点
,
的位置,如图②,平面
平面
,
.
![](https://img.xkw.com/dksih/QBM/2022/1/2/2885752414461952/2885869708861440/STEM/3eb2017726764a4db35dd0fdfba3db38.png?resizew=295)
(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)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4e4aa43d2e64e857267e706e1f50f5c5.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5ef3f82e49ec1a6a12491cb7df944b2d.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/89e9785a8ffb637c91757fe01d3c23a5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b312dab930cbbb9a4bb1a99f044dab73.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b0d7d295ba6f79b1a12eddc9fcc2f59f.png)
![](https://img.xkw.com/dksih/QBM/2022/1/2/2885752414461952/2885869708861440/STEM/3eb2017726764a4db35dd0fdfba3db38.png?resizew=295)
(1)求证:平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81febe64e4bbfb1ed464ec1e1f5667eb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6760f565c694d1cdb6d7068e14526d00.png)
(2)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8637391976e51c3ad50cce5a0a3efa2b.png)
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【推荐3】如图,在四棱锥
中,底面
是直角梯形,且
,
,
,正三角形
所在平面与平面
垂直,
分别为
的中点.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/12/9/1aa39ef5-dcc6-41d0-a592-e4b8a52430de.png?resizew=177)
(1)求证:
平面
;
(2)求二面角
的平面角的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0585b6c0f156eecf9662b9846d4eb693.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f571396be1aa4a8914a66f7d7abd6381.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4a0e5697eca3f5205cb7b343648240bf.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/80f747eb5b2d21c9de962cbfd4ec4bb7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ad056c25c0fdcbcc765eb5cbc6093f2b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08a755679b54c232cbdb8646a8c99e15.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/12/9/1aa39ef5-dcc6-41d0-a592-e4b8a52430de.png?resizew=177)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/21f9157fce2a8339d281178c7c0bccbe.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3e6c2dad46a9052a4185a4f7b4ae8a2e.png)
(2)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4e9d40f58f5fd5fb401a529a42b93ff1.png)
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