如图1,菱形ABCD中∠ABC=120°,动点E,F在边AD,AB上(不含端点),且存在实数
使
,沿EF将△AEF向上折起得到△PEF,使得平面PEF⊥平面BCDEF,如图2所示.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/7/28/fc808256-a8c2-4605-94da-7d42da3a24a5.png?resizew=364)
(1)若BF⊥PD,设三棱锥P-BCD和四棱锥P-BDEF的体积分别为
,
,求
;
(2)当点E的位置变化时,平面EPF与平面BPF的夹角(锐角)的余弦值是否为定值,若是,求出该余弦值,若不是,说明理由;
(3)若AB=2,求四棱锥P-BDEF的外接球半径的最小值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/df64046e91b047037f19e4032e3b6de3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ceeb60f40e8d5b6fc184be29ce3d4bd0.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/7/28/fc808256-a8c2-4605-94da-7d42da3a24a5.png?resizew=364)
(1)若BF⊥PD,设三棱锥P-BCD和四棱锥P-BDEF的体积分别为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c4764374bd2fb78e59cd0b283637baeb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c63055a5d6916f99d07fede49120753f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f737b04ce09bc7e1ed86dc9b3c85203b.png)
(2)当点E的位置变化时,平面EPF与平面BPF的夹角(锐角)的余弦值是否为定值,若是,求出该余弦值,若不是,说明理由;
(3)若AB=2,求四棱锥P-BDEF的外接球半径的最小值.
21-22高一下·重庆沙坪坝·期末 查看更多[2]
更新时间:2022-07-15 13:06:21
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【推荐1】如图1的平行四边形ABCD中,点E为边AB的中点,AB=2,AD=1,∠DAB=60°,现将△ADE沿DE折起,使点A到达点P的位置,得到四棱锥P-BCDE(如图2),使得PC=2.
![](https://img.xkw.com/dksih/QBM/2022/4/21/2962989822238720/2964256605618176/STEM/bf4609dd052f408eb0b9d96ec4c98ffb.png?resizew=378)
(1)证明:CE⊥平面PED;
(2)求三棱锥P-CDE的体积.
![](https://img.xkw.com/dksih/QBM/2022/4/21/2962989822238720/2964256605618176/STEM/bf4609dd052f408eb0b9d96ec4c98ffb.png?resizew=378)
(1)证明:CE⊥平面PED;
(2)求三棱锥P-CDE的体积.
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【推荐2】已知正四面体
的棱长为3,点
在棱
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在线段
上,且
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的中点处,求证:
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(2)如图2,若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/71fa9bb19d1d32270248f377363cd96a.png)
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(3)如图3,当点
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【推荐1】已知矩形ABCD的边AB=2,BC=1,以A为坐标原点,AB,AD边分别在x轴、y轴的正半轴上,建立直角坐标系.将矩形折叠,使A点落在线段DC上,重新记为点![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a18722354086c42e62334983fc50eb6a.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a18722354086c42e62334983fc50eb6a.png)
(1)当点
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c8443c3db3374edb86b0db03d6ed3f1b.png)
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【推荐2】已知正三棱锥的高为1,底面边长为
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【推荐3】如图,在四棱锥
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(1)证明:
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【推荐1】如图,等腰梯形
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的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f571396be1aa4a8914a66f7d7abd6381.png)
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(1)证明:平面
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b4eb7e9ad5486cf1c5e506b20c5469e8.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
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【推荐2】在长方体
中,
为棱
上的点,
,
,
.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/3/14/dd6bc6f9-80c9-4708-bddc-18e4fde28b43.png?resizew=180)
(1)求点
到平面
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e09725691ee7851f54c0dee86b2bf55.png)
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![](https://img.xkw.com/dksih/QBM/editorImg/2023/3/14/dd6bc6f9-80c9-4708-bddc-18e4fde28b43.png?resizew=180)
(1)求点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/97c01fdc7bc471af0b264a04aef0823e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fb5a463a03c549b0dba6d90e7f16a2af.png)
(2)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e06f1a66e6285f78ea5364fb62ac8464.png)
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