下面左边的平行四边形ABCD是由6个正三角形构成,将它沿虚线折起来,可以得到如右图所示的粽子形状的六面体,在这个六面体中,AB与CD夹角的余弦值是( ).
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/19/f0fb3eee-8dc4-47fb-aef7-72f53cf25b76.png?resizew=216)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/19/f0fb3eee-8dc4-47fb-aef7-72f53cf25b76.png?resizew=216)
A.0 | B.1 | C.![]() | D.![]() |
更新时间:2019-01-29 09:43:13
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【推荐1】给定下列两个关于异面直线的命题:命题Ⅰ :若平面
上的直线
与平面
上的直线
为异面直线,直线
是
与
的交线,那么,
至多与
、
中的一条相交;命题Ⅱ :不存在这样的无穷多条直线,它们中的任意两条都是异面直线.
那么,( ).
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e170f206fdbbd834aad7580c727e2cc6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5b5858ee1ce52b251816757257a11c29.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c94bb12cee76221e13f9ef955b0aab1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/071a7e733d466949ac935b4b8ee8d183.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e170f206fdbbd834aad7580c727e2cc6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5b5858ee1ce52b251816757257a11c29.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/071a7e733d466949ac935b4b8ee8d183.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c94bb12cee76221e13f9ef955b0aab1.png)
那么,( ).
A.命题Ⅰ 正确,命题Ⅱ 不正确 | B.命题Ⅱ 正确,命题Ⅰ 不正确 |
C.两个命题都正确 | D.两个命题都不正确 |
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【推荐2】一个空间几何体的三视图如图所示,则该几何体的体积为
![](https://img.xkw.com/dksih/QBM/2018/12/13/2095793884413952/2096829543874560/STEM/76266c121bc540c7a36cada7e879b566.png?resizew=314)
![](https://img.xkw.com/dksih/QBM/2018/12/13/2095793884413952/2096829543874560/STEM/76266c121bc540c7a36cada7e879b566.png?resizew=314)
正(主)视图 侧(左)视图 俯视图
A.![]() | B.![]() |
C.![]() | D.![]() |
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【推荐1】如图,已知正方体
中,
、
分别是
、
的中点.则平面
与平面
所成二面角的平面角的正弦值为.
![](https://img.xkw.com/dksih/QBM/2018/12/14/2096468374495232/2097489469980672/STEM/14761db1282e48f8b5ce3c2c8409b494.png?resizew=169)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e09725691ee7851f54c0dee86b2bf55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2777840758e70e7dbbc18cef8f3d6d2b.png)
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A.![]() | B.![]() | C.![]() | D.1 |
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【推荐2】已知平行六面体
中,以顶点
为端点的三条棱长都等于1,且两两夹角都是60°,则对角线
的长是( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e09725691ee7851f54c0dee86b2bf55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/24bb49fdc6b6bbb2449fdf8a0de769d3.png)
A.![]() | B.![]() | C.![]() | D.6 |
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【推荐1】如图,在直三棱柱
中,
,
、
分别是
、
的中点,如果对线段
上任意一点
,都有
,则
等于( )
![](https://img.xkw.com/dksih/QBM/editorImg/2023/1/3/185782b1-ad10-49a7-a985-2abe3e63847d.png?resizew=132)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42d3a82b8e587ee890467835bc4e854c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ea02cbe8d8991fe4fead6cf4a5880b83.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/acc290b44635265137fdf13146b6a6d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d88bf46ad08f9677c37eed1d0369329.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/11ddc92d84d188c66b435664a7e7b5a4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
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![](https://img.xkw.com/dksih/QBM/editorImg/2023/1/3/185782b1-ad10-49a7-a985-2abe3e63847d.png?resizew=132)
A.![]() | B.![]() |
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【推荐2】正四棱锥
的五个顶点在同一个球面上,若该正四棱锥的底面边长为4,侧棱长为
,则球的表面积为.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0585b6c0f156eecf9662b9846d4eb693.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b10e8abf8690e4b129466ddb918bcc94.png)
A.![]() | B.![]() |
C.![]() | D.![]() |
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