名校
解题方法
1 . 如图,在直三棱柱
中,
,
,M为AB的中点,D在
上且
.
(1)求证:平面
平面
;
(2)求直线CM与平面CBD所成角的正弦值;
(3)求二面角
的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42d3a82b8e587ee890467835bc4e854c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ed10df4140819d5451773a45de66201b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/836454922ab97fd8e2603eb05d19eed4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/11ddc92d84d188c66b435664a7e7b5a4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5355da4203567ad145f6fabd226405a0.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/11/17/5f9cbbe0-316b-448c-870e-fde2185bf708.png?resizew=149)
(1)求证:平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/268be8b7f83cbdf253b1e05e09cbbad7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ab3e0dba5705e1d749cfb21ebbb2ed93.png)
(2)求直线CM与平面CBD所成角的正弦值;
(3)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/30e536ceabd66ab4850e9207bf8e6e4c.png)
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名校
解题方法
2 . 在棱长为2的正方体
中,点M是对角线
上的点(点M与A、
不重合),则下列结论正确的是______________ .(请填写序号)
①存在点M,使得平面
平面
;
②存在点M,使得
平面
;
③若
的面积为S,则
;
④若
、
分别是
在平面
与平面
的正投影的面积,则存在点M,使得
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e09725691ee7851f54c0dee86b2bf55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/24bb49fdc6b6bbb2449fdf8a0de769d3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b1241216f3c1cb5e73043dd1037f556d.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/11/8/ff785f15-c66b-43ee-bd82-a02f45c1820f.png?resizew=157)
①存在点M,使得平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dba49eb8ddd4dd38c1f994ccec93430e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a935b7d21a103a264b6e96ecf82dbe4a.png)
②存在点M,使得
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0457394ce4f2dc8d940c565c94dcf557.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b0a582c36d62d83c16425b2f54b4354.png)
③若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ce447afe4b0bb57a844b2c103b55fc71.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42910d271417cc2435d0affa6c85afd5.png)
④若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e097c8d4c948de063796bd19f85b3a9a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1e0bd63f55069a3bc870915010b39225.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ce447afe4b0bb57a844b2c103b55fc71.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/632f2bf1cd0435041fa04b01901d1c8c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/58cc6184b191e6da43911e701121517e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/31dd78e9156dcf6db93f6cbcc5b43b14.png)
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