已知正三棱锥
中,
,
是
的中点,则异面直线
与
所成角的余弦值为___________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/891579e7c231584a8e16b8eeff79888e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b1affed1ad8e53a73308c85849a72444.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85c4bdfb0db1e31e8459df1d15f9ab55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
更新时间:2021-07-10 11:29:16
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相似题推荐
填空题-单空题
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【推荐1】如图所示,在正方体
中,
,
分别为棱
,
的中点,有以下四个结论:
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/12/3da75f0c-a7bb-4c59-895a-cd2749a2be2b.png?resizew=144)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e09725691ee7851f54c0dee86b2bf55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54a5d7d3b6b63fe5c24c3907b7a8eaa3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f66fb71b75b63594ebeeeebd1963eed5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/53e97fcdcfd6183b976a61ef3222c607.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/12/3da75f0c-a7bb-4c59-895a-cd2749a2be2b.png?resizew=144)
①直线与
是相交直线;
②直线与
是平行直线;
③直线与
是异面直线;
④直线与
所成的角为
.
其中正确的结论为
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【推荐2】如图,在正方体
中,M,N分别为AC,
的中点,则异面直线MN与
所成的角为______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e09725691ee7851f54c0dee86b2bf55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e26d9636ad77369535852c6e4493446a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/22adbc0da438220f9cace11b629d799b.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/8/1/5ef44427-ae1d-4717-856d-343053baad00.png?resizew=210)
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【推荐1】已知下列四个命题:
直线
与平面
内的无数条直线垂直,则
;
若
,则
;
若
,则
;
在
中,若
,则
;
其中真命题的个数__________ .(请用数字作答)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6a617a9b648bfb804eb7ac1cf357f8a8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f85fca60a11e1af2bf50138d0e3fe62.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e170f206fdbbd834aad7580c727e2cc6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9e380108ba2cf04e68a5a9393d2b921c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f731aa23c326a79f5a97c0b805166272.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7edecfbf1b4e1052468d209e8f017a88.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f612ce3b03a5fdb56ee5f347407f02e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1ae3c3c8f3d94894cbd783960ca9c8a1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2bd3334b794e7c2806a6dcc32008f2ab.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4be21ba40cfe9cf741e529b73328d7ae.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/428f740d77d1a1f4303effd6c1e87028.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ca51be437b1a97ca92aa1159ab71102c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/19dc38d888741a1b2e95fe0773a48c38.png)
其中真命题的个数
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解题方法
【推荐2】“加工六角螺母,只需六个侧面都是矩形,那么六条侧棱一定都垂直于上下两面”,这个论断用到了什么原理______ .
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【推荐1】如图,在三棱锥
,
平面
,点E、F(E与A、D不重合)分别在棱
、
上,且
.则下列结论中:正确结论的序号是________ .
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/14/22c2cbff-660c-4310-9238-a9f807fb4676.png?resizew=159)
①
//平面
;
②
;
③
//
;
④直线
与
的距离等于直线
与
的距离.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/891579e7c231584a8e16b8eeff79888e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c394c03f93a8ee828e61832bce6e56b3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7abd284f76d9f5769bc189508ce2572b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ab1a1fd2fc33e89f357cef772ff6cd0e.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/14/22c2cbff-660c-4310-9238-a9f807fb4676.png?resizew=159)
①
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
②
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/35333abd7f02d663d15251bc5cbbf921.png)
③
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
④直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
您最近一年使用:0次
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【推荐2】如图,已知四棱锥
,底面
为正方形,
平面
,给出下列命题:
![](https://img.xkw.com/dksih/QBM/2021/7/9/2760753412734976/2764614432997376/STEM/2667a584-2f22-419c-9fca-80840751be7e.png?resizew=296)
①图中所有线段中
最长
②
可能为直角三角形
③平面
与平面
的交线与
平行
其中正确的序号是_____
![](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/ccd4fd4b7a4d6b8ca0c5827c055a9ce7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://img.xkw.com/dksih/QBM/2021/7/9/2760753412734976/2764614432997376/STEM/2667a584-2f22-419c-9fca-80840751be7e.png?resizew=296)
①图中所有线段中
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48f3c9abbd78e9a6840ee5f30381daac.png)
②
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/acee03d4bb4667b6c345221b6c9b0fa4.png)
③平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1e582d73b96ba649378379c3074d506d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/80f747eb5b2d21c9de962cbfd4ec4bb7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
其中正确的序号是
您最近一年使用:0次