如图,在棱长为1的正方体
中,点
在
上移动,点
在
上移动,
,连接
.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/1/4/63e41f0e-08fe-4c7c-a589-666b7c8c3972.png?resizew=177)
(1)证明:对任意
,总有
∥平面
;
(2)当
的长度最小时,求二面角
的平面角的余弦值.
![](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/83c09eec4e14a861af83d7828797d176.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54a5d7d3b6b63fe5c24c3907b7a8eaa3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/039d7699ed888e784646995d23061703.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411461db15ee8086332c531e086c40c7.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/1/4/63e41f0e-08fe-4c7c-a589-666b7c8c3972.png?resizew=177)
(1)证明:对任意
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3a3ce5abb6b25b37642d7322dcbe77cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411461db15ee8086332c531e086c40c7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7b54387f870ae37f7951b253665d64f6.png)
(2)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411461db15ee8086332c531e086c40c7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/70682f6196e6c1a08eb48da73e8919ca.png)
更新时间:2019-10-22 08:30:23
|
相似题推荐
解答题-证明题
|
适中
(0.65)
解题方法
【推荐1】如图,在多面体
中,四边形
是正方形,
为
的中点.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/8/10/d8cf2471-850b-4fb8-9ac5-0f2e801ed986.png?resizew=220)
(1)求证:
平面
;
(2)若
,求三棱锥
的体积.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9165d9bfbb0f0d19eb482c2a4c1b29b7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b32c05247f6998d7a70d31d13be4148c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/12bf57114017b93e0456d7c49198bb0c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/8/10/d8cf2471-850b-4fb8-9ac5-0f2e801ed986.png?resizew=220)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/55537f7dbac74c17fe0dc386dcdab3fa.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0fa3254460ecbacecb3e57c5dce227f4.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1bea000405c2144c102a915d464f45b0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d3b635e62c3b1f4a57feac8d22be84ee.png)
您最近一年使用:0次
解答题-问答题
|
适中
(0.65)
解题方法
【推荐2】已知四棱锥
,底面
是
、边长为2的菱形,又
,且
,点
分别是
的中点.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/8/8ec9b573-d969-4bbb-b6fe-ff3c63e0c251.png?resizew=182)
(1)证明:DN//平面PMB;
(2)证明:平面PMB
平面PAD;
(3)求二面角
的余弦值.
![](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/c5b8b98b2f83279a49e94d9f48c5e6f2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/29f7578593106063dbf3b13de6f4f280.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/37e2267c84394668eff2e9f5918de4fb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6670479a0083dd2dfd5ad55b47b1ab6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0c129fb303ad849a73ef59e5de105fd5.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/8/8ec9b573-d969-4bbb-b6fe-ff3c63e0c251.png?resizew=182)
(1)证明:DN//平面PMB;
(2)证明:平面PMB
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1633988fd62a652de726ee92a917b52d.png)
(3)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/87aed767c861502aff771e6b0114746c.png)
您最近一年使用:0次
解答题-问答题
|
适中
(0.65)
名校
解题方法
【推荐1】如图,斜三棱柱
的棱长均为2,侧面
底面
,且
.
![](https://img.xkw.com/dksih/QBM/2021/2/7/2653155599892480/2663360482672640/STEM/5d14dc00-484a-44f8-9a53-b5b5e98f29aa.png?resizew=233)
(1)求直线
与侧面
所成角的正弦值;
(2)求二面角
的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42d3a82b8e587ee890467835bc4e854c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/37ab9019b1b3ff14f7ec329936108c2c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48f95a09aa385a3591facd2132dde809.png)
![](https://img.xkw.com/dksih/QBM/2021/2/7/2653155599892480/2663360482672640/STEM/5d14dc00-484a-44f8-9a53-b5b5e98f29aa.png?resizew=233)
(1)求直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/24bb49fdc6b6bbb2449fdf8a0de769d3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9961e091f180e964a962adf6916f33c8.png)
(2)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6997af36a239195f7b55557242cb03c4.png)
您最近一年使用:0次
解答题-证明题
|
适中
(0.65)
【推荐2】如图,在平面四边形
中,
和
都是等腰直角三角形且
,正方形
的边
.
(1)求证:
平面
;
(2)求二面角
的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2dde327febef2331a4766a79b433cc02.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e742966e3711cfa53dce04022acf4bcc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ca2698f08d94afa1cd5b81444791f4c7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/481f38563c5191cb433ffc0c739ff761.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7a47dcb24ffe20e8153e0d113ff8bee3.png)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4a5f445af1ae136773cb338920552ff2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/500df0e782bb081e608f4bc1d576afcf.png)
(2)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d9b123303738a595ec0126beb0fa64a8.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/10/31/00a4d9e8-def0-4d6b-b3f5-f39839581a92.png?resizew=203)
您最近一年使用:0次