在如图所示几何体中,四边形ABCD与ABEF均为直角梯形,
,
,
,
,且平面
平面
.已知
,
.
![](https://img.xkw.com/dksih/QBM/2022/3/22/2941844135526400/2942672629096448/STEM/51158afb-9e2e-4d85-9b35-03457f104978.png?resizew=189)
(1)证明:
;
(2)求直线EF与平面BEC所成角的正弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b0fff774b4b0087a6f304ce930d359be.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d61d846cbc5220533271c962b85c4b5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1134c8e3440abb6cd385af2c169037fe.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4eed15d0ed75bf936f224f931da5d950.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4cf9a6db3571fa57bfa2d5e4d44c51b3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2dde327febef2331a4766a79b433cc02.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/19bebae04c72b934bfbbf0b4d01f164f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5c8bf5571150ab2974b6471d9b837a7.png)
![](https://img.xkw.com/dksih/QBM/2022/3/22/2941844135526400/2942672629096448/STEM/51158afb-9e2e-4d85-9b35-03457f104978.png?resizew=189)
(1)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/93f6382a8285b7e7bfe642b7158e55df.png)
(2)求直线EF与平面BEC所成角的正弦值.
更新时间:2022-03-23 23:05:42
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【推荐1】如图所示,在三棱柱
中,侧面
是矩形,
,
,
是
的中点,
与
交于
,且
面
.
![](https://img.xkw.com/dksih/QBM/2020/11/13/2592139080335360/2603466374324224/STEM/7621bbb02f5741a28f04717458d8b038.png?resizew=244)
(1)求证:
;
(2)若
,求二面角
的正弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42d3a82b8e587ee890467835bc4e854c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ab3e0dba5705e1d749cfb21ebbb2ed93.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2777840758e70e7dbbc18cef8f3d6d2b.png)
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(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7768503b1ad4775258b2f1a71c413086.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f842145a92b63d04c0fe88001f01d31e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ab6d47edbcc2ae6efcfd7f28e401e3e9.png)
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【推荐2】已知正方形
所在平面外一点P满足
平面
,E,F分别是
的中点.
(1)求证:
∥平面
;
(2)若
,求
与
所成角的大小.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ccd4fd4b7a4d6b8ca0c5827c055a9ce7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6fbb19cb4eb2d7f3207559eb07355ba2.png)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/852aabd89edffc1b94344ff3f1f31ccd.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0498b9374bee2169d323c3bd8d2d23d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6aa2b5e09f8ec785c59900a529390a02.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
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【推荐1】如图①,在等腰直角三角形
中,
分别是
上的点,且满足
.将
沿
折起,得到如图②所示的四棱锥
.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/1/30/8cb8d241-d5f8-4267-8552-8b44da6a4fc1.png?resizew=278)
(1)设平面
平面
,证明:
⊥平面
;
(2)若
,求直线
与平面
所成角的正弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e230d68009af8089d421a360a3d42373.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d0ac36c7ac328d903073739b8dcc0531.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/1/30/8cb8d241-d5f8-4267-8552-8b44da6a4fc1.png?resizew=278)
(1)设平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a8dc5f056a7b84dc39d5ce46e615e91d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/304d6b84040aa3ec0078de3451f02db7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f85fca60a11e1af2bf50138d0e3fe62.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8e106f4233be16e98f2c1bf9f1635622.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8fb4e94b009c6502fba0c730fe7e2c59.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e0629ce42392a7fe9be21d25c39c3e64.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4739ad948445af72d585fe29c745929b.png)
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【推荐2】如图,在四棱锥
中,平面
平面
为等边三角形,底面
为等腰梯形,
,且
.
(1)在棱
上是否存在点
,使得
平面
?若存在,请确定点
的位置;若不存在,请说明理由;
(2)求
与平面
所成角的正弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0585b6c0f156eecf9662b9846d4eb693.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e4aa9084b8fe0fe05c4388d1f835587b.png)
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![](https://img.xkw.com/dksih/QBM/editorImg/2023/11/19/b35d166d-92cd-4988-8da1-1d44ef5dadf7.png?resizew=145)
(1)在棱
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d2be49c37e30a3ced0364c3e74d8c687.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/852aabd89edffc1b94344ff3f1f31ccd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
(2)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48f3c9abbd78e9a6840ee5f30381daac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/852aabd89edffc1b94344ff3f1f31ccd.png)
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【推荐3】如图,四棱锥
中,侧面
为等边三角形且垂直于底面
,
,
,E是PD的中点.
(1)证明:
平面
;
(2)当点
为棱
中点时,求直线
与平面
所成角的正弦值.
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(1)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/11d27ff0b39832f094ec51e28721d739.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1e582d73b96ba649378379c3074d506d.png)
(2)当点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48f3c9abbd78e9a6840ee5f30381daac.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1e582d73b96ba649378379c3074d506d.png)
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