已知△ABC为等腰直角三角形,AC=BC=4,E,F分别为AC和AB上的点,且AE=1,EF∥BC,如图1.沿EF将△AEF折起使平面AEF⊥平面BCEF,连接AC,AB,如图2.
![](https://img.xkw.com/dksih/QBM/2022/1/4/2887316860796928/2921470059315200/STEM/3f6db842-7228-4082-8b0a-43a53bc8b615.png?resizew=360)
(1)求异面直线AC与BF所成角的余弦值;
(2)已知M为棱AC上一点,试确定M的位置,使EM∥平面ABF.
![](https://img.xkw.com/dksih/QBM/2022/1/4/2887316860796928/2921470059315200/STEM/3f6db842-7228-4082-8b0a-43a53bc8b615.png?resizew=360)
(1)求异面直线AC与BF所成角的余弦值;
(2)已知M为棱AC上一点,试确定M的位置,使EM∥平面ABF.
更新时间:2022-02-22 00:08:57
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【推荐1】在三棱锥
中,OA、OB、OC所在直线两两垂直,且
,CA与平面AOB所成角为
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的体积是
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(1)求三棱锥
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(2)在线段CA上取一点E,当E在什么位置时,异面直线BE与OD所成的角为
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7ebc9b785a6bbb0ce1256a9e1ecc68f4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9fca3734de79f7f50b552ef62b29dc7c.png)
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![](https://img.xkw.com/dksih/QBM/2020/1/12/2375692714270720/2376066405949440/STEM/aeb67cf4db314ff8a456671afa6920c5.png?resizew=152)
(1)求三棱锥
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7ebc9b785a6bbb0ce1256a9e1ecc68f4.png)
(2)在线段CA上取一点E,当E在什么位置时,异面直线BE与OD所成的角为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/817c2109ca77615fa62754c71d1238f6.png)
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解题方法
【推荐2】如图,在直三棱柱
中,
,
,
,求异面直线
与
所成角的度数.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/28/a14f424f-9b52-4a0e-8a2e-72d2d871c1a7.png?resizew=148)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42d3a82b8e587ee890467835bc4e854c.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4ef8866ccf160ddc441bf69c5d3a3d5a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/36c4559d27e3905980d1a4f1856f07de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0d8772aa893a9c1d40f714cb25701701.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
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解答题-问答题
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名校
【推荐1】已知四棱锥
的底面是菱形,对角线
、
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![](https://img.xkw.com/dksih/QBM/2021/6/17/2744725208121344/2749792864141312/STEM/ecf27a49-8009-4453-976b-a6f51ad9d4b0.png?resizew=222)
(1)若三棱锥
体积是
,求
的值;
(2)若直线
与平面
所成角的正弦值是
,求
的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0585b6c0f156eecf9662b9846d4eb693.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
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(1)若三棱锥
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e76f6552e20faeba98588e9b5dd01f6e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5b282c337227aa697d420b8c3c8d4309.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/df64046e91b047037f19e4032e3b6de3.png)
(2)若直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bd33764ff4efddfe11a98a609753715c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9af29254fe60a392c249c5791279e9c8.png)
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【推荐2】如图,在多面体
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,
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(1)若点F为
的中点,证明:
平面
;
(2)若直线
与平面
所成的角为
,求平面
与平面
所成的角(锐角)的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9142a8490de14a87eda628ffa7e28982.png)
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(1)若点F为
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4a5f445af1ae136773cb338920552ff2.png)
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(2)若直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85c4bdfb0db1e31e8459df1d15f9ab55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
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解答题-证明题
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【推荐3】如图,在四棱锥
中,底面
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a9bfa68259d7a331be323b2038d628a.png)
,
,
,
,
平面
,且
,点
在棱
上,点
为
中点.
(1)证明:若
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平面
;
(2)求二面角
的正弦值;
(3)是否存在点
,使
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的值;若不存在,说明理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0585b6c0f156eecf9662b9846d4eb693.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2024/1/5/60e825cb-0b09-4506-8e0c-a91f70113347.png?resizew=168)
(1)证明:若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fc85ce5e111acf7162b8e1b5a3f6b220.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411461db15ee8086332c531e086c40c7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a9bfa68259d7a331be323b2038d628a.png)
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(2)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ed1000f47a7a77a81c2d0bf1b1f8599f.png)
(3)是否存在点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/80f747eb5b2d21c9de962cbfd4ec4bb7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0467b0675c3ecfb282cc88255284d3e1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/47548785e478bc5b9591341a881e3127.png)
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