如图,棱长为4的正方体
中,P为线段
的中点,M,N分别为线段
和棱
上任意一点,则
的最小值为______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e09725691ee7851f54c0dee86b2bf55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b470c4e195cf7a07b7a331ce4b436e03.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/24bb49fdc6b6bbb2449fdf8a0de769d3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/56f7ba05c54b3de1f4378f7c8eb58328.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2ccb7afc3c4ff8663765eaf30c8fdcbc.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/7/31/0caa7d0e-2561-4b8e-9c7e-9641ce08386c.png?resizew=155)
更新时间:2023-07-29 13:42:02
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【推荐1】二面角
的大小为
为垂足,
为垂足,
是棱上动点,则
的最小值为_______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c9337f03fddaf2467198f4e8b5358eb6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e57db770e96adfb842e603d0fbc13c2e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0dbced4d87388825f4b44e44882e5ce.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b4ac58af1cb8cc075c1352a730438dad.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f61ec7cb63b762551db9f3ab79b3aa4.png)
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【推荐2】如图,在长方体
中,![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0d64cb550b33c5ca0d4aceb158ff028.png)
点
为线段
上的动点(包含线段端点),则
的周长的最小值是_____________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0d64cb550b33c5ca0d4aceb158ff028.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bbfc2e4f8c26d5b20926196833fa5ecc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3ee8456443402a25b1e25d35ff7e1c98.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7616ae6c1512e837900c067f6b190dbc.png)
![](https://img.xkw.com/dksih/QBM/2017/11/10/1814292395573248/1815464619122688/STEM/d56976fd554b415ba3af2cf810dd917b.png?resizew=188)
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解题方法
【推荐1】如图所示,在长方体
中,
,点
是棱
上的一个动点,若平面
交棱
于点
,给出下列命题:
![](https://img.xkw.com/dksih/QBM/editorImg/2022/10/27/cc4fce1e-276b-4eed-9181-b794bbb34d6d.png?resizew=184)
①四棱锥
的体积恒为定值;
②存在点
,使得
平面
;
③对于棱
上任意一点
,在棱
上均有相应的点
,使得![](https://staticzujuan.xkw.com/quesimg/Upload/formula/abf80148409afb32ced0b4f59f1ba709.png)
平面
;
④存在唯一的点
,使得截面四边形
的周长取得最小值.
其中真命题的是_____________ . (填写所有正确答案的序号)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/00b378805114b83f76fcece53698a28d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dce95726804cf91de63f07b37c65da6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/252053b853152bd294a8315debd00b92.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cbb16f7dbc4b9993c4efa0764df1d8ca.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d6e92aadc02ae971ed29bb2db51b012f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e17230625e72d3a9c6d72ff61019ff61.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/655b6a742dbacdab5aaa298007663dd4.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/10/27/cc4fce1e-276b-4eed-9181-b794bbb34d6d.png?resizew=184)
①四棱锥
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fb7c649d4bbd61eaef51e529ef9b1204.png)
②存在点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/252053b853152bd294a8315debd00b92.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/29bac4ff764651106d9ab46855f20331.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7759e75f16985d39b854e45774f06a86.png)
③对于棱
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cbb16f7dbc4b9993c4efa0764df1d8ca.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/252053b853152bd294a8315debd00b92.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b4c23c66ab7d74f51cb4b79d1029fb38.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/afc3e8a1475b983d1a4295db0e16d4c2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/abf80148409afb32ced0b4f59f1ba709.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7003aee0b4b85f0fdd48ca9ae5826d54.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85bed42b435afda8e8c47dd0da8e4a1f.png)
④存在唯一的点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/252053b853152bd294a8315debd00b92.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/422676748fd5d893c0e4331fee24e473.png)
其中真命题的是
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【推荐2】如图,已知四面体.的棱
平面
,且
,其余的棱长均为
.四面体
以
所在的直线为轴旋转
弧度,且始终在水平放置的平面
上方.如果将四面体
在平面
内正投影面积看成关于
的函数,记为
,则函数
的最小值为
;
的最小正周期为
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/307807ee10071bafbe922eb18d2517d7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e170f206fdbbd834aad7580c727e2cc6.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/782e6aab135b30eed10b49df5a91988d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/782e6aab135b30eed10b49df5a91988d.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/836f2cd7c1bf45a865b7d6bcb3e8f2d5.png)
![](https://img.xkw.com/dksih/QBM/2019/5/5/2196925960151040/2198657068802049/STEM/3a94a605-84aa-4ed0-bf67-2902e5ae1439.png)
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【推荐3】在如图所示的棱长为2的正方体
中,作与正方体体对角线
垂直的平面
,(1)三棱锥
的外接球的表面积为___________ ;(2)平面
与正方体的截面面积最大值为___________
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e09725691ee7851f54c0dee86b2bf55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/87cdc08e1c4a04a18d5ecea03393e36d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e170f206fdbbd834aad7580c727e2cc6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1e6218366c67f4b601af1abbdcf7524b.png)
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