已知正方形的边长为4,E、F分别为AD、BC的中点,以EF为棱将正方形ABCD折成如图所示的60°的二面角,点M在线段AB上.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/5/c5cf9ec8-d9f2-4130-9e7a-9581944b2660.png?resizew=275)
(1)若M为AB的中点,且直线MF与由A,D,E三点所确定平面的交点为O,试确定点O的位置,并证明直线OD∥平面EMC;
(2)是否存在点M,使得直线DE与平面EMC所成的角为60°?若存在,求线段AM的长,若不存在,请说明理由.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/5/c5cf9ec8-d9f2-4130-9e7a-9581944b2660.png?resizew=275)
(1)若M为AB的中点,且直线MF与由A,D,E三点所确定平面的交点为O,试确定点O的位置,并证明直线OD∥平面EMC;
(2)是否存在点M,使得直线DE与平面EMC所成的角为60°?若存在,求线段AM的长,若不存在,请说明理由.
更新时间:2022-12-05 10:19:57
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解答题-证明题
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适中
(0.65)
解题方法
【推荐1】已知直三棱柱
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是
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(1)求三棱柱
的体积;
(2)求证:
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(3)求证:
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2777840758e70e7dbbc18cef8f3d6d2b.png)
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(1)求三棱柱
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42d3a82b8e587ee890467835bc4e854c.png)
(2)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/24a8670759c61d785b9a336885df700b.png)
(3)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
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【推荐2】如图,平面
平面
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、
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(1)设平面
平面
,判断直线l与
的位置关系,并证明;
(2)求直线
与平面
所成角的正弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6d077f6da8b2c00b152d4679aa2ed7f7.png)
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(1)设平面
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(2)求直线
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解答题-问答题
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(0.65)
解题方法
【推荐1】已知三棱柱
各棱长均为2,且
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(1)求
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上是否存在一点
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?若存在,给出点
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42d3a82b8e587ee890467835bc4e854c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a18722354086c42e62334983fc50eb6a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
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![](https://img.xkw.com/dksih/QBM/editorImg/2023/3/21/e23a2ac1-ac16-4aa8-8e77-4f2c9ddf35c6.png?resizew=141)
(1)求
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(2)线段
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
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【推荐2】如图1,矩形ABCD,点E,F分别是线段AB,CD的中点,
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![](https://img.xkw.com/dksih/QBM/editorImg/2023/2/6/f4289d06-b7a3-440e-9930-5d299e03ba32.png?resizew=398)
(1)若所成二面角的大小为
(如图2),求证:直线
面DBF;
(2)若所成二面角的大小为
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的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b58022e20e4bd2a6c25f3f3a2d14fb76.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/2/6/f4289d06-b7a3-440e-9930-5d299e03ba32.png?resizew=398)
(1)若所成二面角的大小为
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(2)若所成二面角的大小为
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