名校
1 . 如图,矩形ABCD中,AB=2AD,E为边AB的中点.将
ADE沿直线DE翻折成
A1DE(A1
平面BCDE).若M在线段A1C上(点M与A1,C不重合),则在
ADE翻折过程中,给出下列判断:
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/18/6c74a8b1-9cce-4664-af4e-7f1442648b97.png?resizew=223)
①当M为线段A1C中点时,|BM|为定值;
②存在某个位置,使DE
A1C;
③当四棱锥A1—BCDE体积最大时,点A1到平面BCDE的距离为|A1H|(DE的中点为H);
④当二面角A1—DE—B的大小为
时,异面直线A1D与BE所成角的余弦值为
.
其中判断正确的个数为( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ce4cba95fc7d4853a243f8e3fb20ce70.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ce4cba95fc7d4853a243f8e3fb20ce70.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e581739cffb5676d997a58ab10d58880.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ce4cba95fc7d4853a243f8e3fb20ce70.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/18/6c74a8b1-9cce-4664-af4e-7f1442648b97.png?resizew=223)
①当M为线段A1C中点时,|BM|为定值;
②存在某个位置,使DE
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1633988fd62a652de726ee92a917b52d.png)
③当四棱锥A1—BCDE体积最大时,点A1到平面BCDE的距离为|A1H|(DE的中点为H);
④当二面角A1—DE—B的大小为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac1a63ab608517bb10aa036783dfb51f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/457eed9a9809a61c38d9143c00d311b5.png)
其中判断正确的个数为( )
A.1 | B.2 | C.3 | D.4 |
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2021-07-04更新
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2卷引用:天津市滨海新区2020-2021学年高一下学期期末数学试题