如图,矩形
的边
,
,
平面
,
,点E在CD上,若
,则
___________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d2c15801fee2405573677484f5dcfa4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/09d27bd71d79cb19eb554175e4ef0867.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ccd4fd4b7a4d6b8ca0c5827c055a9ce7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/491c3a4f72b84ebadd28b90711435adc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/80ca27617694319e68fdec8fdb11c099.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f75158101661ac908d605abfe2048226.png)
![](https://img.xkw.com/dksih/QBM/2021/11/18/2853843550601216/2859050132733952/STEM/e04540fa-07a3-4807-bde0-720dac71938e.png?resizew=238)
更新时间:2021-11-25 19:35:17
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【推荐1】已知三棱锥
中,
,
是边长为
的正三角形,则三棱锥
的外接球半径为__________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63397cda22cb1fad59cf966dfb588643.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d2a86333628c0e0fed6523b5c03cf157.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0faed94a64b2dcfc6801b4fca0f16675.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a7ffe8515ff6183c1c7775dc6f94bdb8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63397cda22cb1fad59cf966dfb588643.png)
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【推荐2】
中,
,作
,点
为垂足,
为
在
上的射影,
为
在
上的射影,则有
成立.直角四面体
(即
)中,点
为点
在平面
内的射影,
的面积分别为
,且
在平面
内的射影分别为
、
,其面积分别为
的面积记为
,类比直角三角形中的射影结论,在直角四面体
中可得到的正确结论为______ .(写出一个正确结论即可).
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1ce7f6d278f2ef7a193b7eed7be6b3c5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6f8e9ec412ea0355e4e5cd06c60e5fee.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b5f215a42c4b7078d8d65923eb9980e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a6fc3d6ccd1273f5264fbe379917ac32.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63397cda22cb1fad59cf966dfb588643.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a9b32d28f87339224b79072f83005d68.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/31c80eb47003139afbff206cad09442c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fcf4e20ea341827ce5f9552daee39462.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/31c80eb47003139afbff206cad09442c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/257e807bf73207b5cd35a19a6c023bbc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2bbf9680f74a9ac5d934304654ce2771.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a43295b4f7d1d1750d56bec08ba7b0c6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf231f8f86fb922df4ca0c87f044cec3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63397cda22cb1fad59cf966dfb588643.png)
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【推荐1】在四棱锥P-ABCD中,底面是边长为2的正方形,PA⊥底面ABCD,E为BC的中点,PC与底面所成角为
,则点E到平面BDP的距离为________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/717d026dd0029aab76fd410d88f67bd8.png)
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【推荐2】如图,矩形
中,
为
的中点,将
沿直线
翻折成
,连结
,
为
的中点,则在翻折过程中,下列说法中所有正确的序号是_______ .
①存在某个位置,使得
;
②翻折过程中,
的长是定值;
③若
,则
;
④若
,当三棱锥
的体积最大时,三棱锥
的外接球的表面积是
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4201d3bead2e48cc80052b1418f23db9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d50703c46b6153945d718b198f03b4b5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/94b3c9e0226017776726688f88f7d5ff.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/87cdc08e1c4a04a18d5ecea03393e36d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54a5d7d3b6b63fe5c24c3907b7a8eaa3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/87cdc08e1c4a04a18d5ecea03393e36d.png)
①存在某个位置,使得
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e0ffdf36ba9697d1fe3376a854c26c01.png)
②翻折过程中,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/167d31eb8432b5c0364316e5048c23dd.png)
③若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/594c95ec1d027b7fa228f341d0b253a3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6bbd93f6ff9ae6a9e1fb55079349694.png)
④若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d73cdecfee3cf9596904484701b79149.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/05b47bffe27791c8a1cbb3180a480d13.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/05b47bffe27791c8a1cbb3180a480d13.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9609625b502348556ff8ba32deac8caa.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/3/3/44a7fd89-8e6f-4933-ae1f-d4bd30bff914.png?resizew=184)
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