如图,多面体EFABCD中,
平面ABCD,底面ABCD为等腰梯形,
,
,
,
,且
.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/1/23/f088f11c-4884-49ba-ae8e-a369eb5eee28.png?resizew=153)
(1)求证:![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4eedae8d316c76e3d0b451256de03fb9.png)
平面BDF;
(2)求平面CBE与平面DBE的夹角的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/147e7c8ba0bbb540a712f6eb2ed6d22e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f571396be1aa4a8914a66f7d7abd6381.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e075468e7fb0bf30229aec01a7205977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a012df371f405b2af80a33ffab9829a6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/66784e61bb8be33243a208895fc2ae08.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/aeedb5f361a1baff6338436fff6c471d.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/1/23/f088f11c-4884-49ba-ae8e-a369eb5eee28.png?resizew=153)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4eedae8d316c76e3d0b451256de03fb9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fb31ef428bd9de9bc875b343feded3c7.png)
(2)求平面CBE与平面DBE的夹角的余弦值.
更新时间:2023-01-19 10:41:52
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【推荐1】在锐角
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【推荐2】在
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【推荐1】如图,在四棱锥
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3e6c2dad46a9052a4185a4f7b4ae8a2e.png)
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解题方法
【推荐2】如图,在四棱锥
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(
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【推荐1】如图,在四棱锥中,
底面
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,
,
,
,E是PC的中点.证明:PD⊥平面ABE.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/9/15/7baee0fc-b5e7-4207-980d-1b76151edddc.png?resizew=183)
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【推荐2】如图所示,在直三棱柱
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;
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.
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(1)
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【推荐3】如图,在四面体
中,
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是
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∥平面
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(2)若
是正三角形,
,且
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夹角的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63397cda22cb1fad59cf966dfb588643.png)
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(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/82465b63174087aeba7788ed984583d2.png)
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【推荐1】如图,在四棱锥
中,四边形
为平行四边形,
,
平面
,
,
.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/10/f5319b89-e797-4560-8295-38443cfce076.png?resizew=184)
(1)求证:
平面
;
(2)求二面角
的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0585b6c0f156eecf9662b9846d4eb693.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/aff72945e22c436363b7bef4dd50af5a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d4f5d8a522f934ef58b2a6007cda874d.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/10/f5319b89-e797-4560-8295-38443cfce076.png?resizew=184)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f3e126c16032892966489053f44b9048.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
(2)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b4daddc615c7b9146bd197509a26d001.png)
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【推荐2】如图,在四棱锥
中,四边形ABCD为正方形,
平面ABCD,
,F是PB中点,
平面PBC;
(2)求二面角
的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0585b6c0f156eecf9662b9846d4eb693.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ccd4fd4b7a4d6b8ca0c5827c055a9ce7.png)
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(2)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/907ff109ed2739140db28bc4b2617bf7.png)
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