如图,在三棱锥
中,
为
的中点,
为
的中点,
为
的中点,
,
,
平面
.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/23/72c5a51e-13cf-4652-883c-b39947d4d354.png?resizew=158)
(1)求证:平面
平面
;
(2)求二面角
的余弦值
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/891579e7c231584a8e16b8eeff79888e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a7a3e0de70e2ecbe377bc8fd89478f16.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fcd0ced286a0fbc7e4862f8147264277.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a7b7675ff57bdccb95a8241c1cd09f05.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/23/72c5a51e-13cf-4652-883c-b39947d4d354.png?resizew=158)
(1)求证:平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/392e71a9d1ebe4577f785581d0142305.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ca67a5b8f69507c8b80379e86f90a8ce.png)
(2)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/704a0bd2d4cc6b98ca2a2ab3fe0c81da.png)
更新时间:2020-06-15 19:17:00
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【推荐1】如图,在四棱锥
中,平面
平面
,
,点
分别为
的中点.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/6/86d4b6bb-f892-4412-9cbb-c53216c52605.png?resizew=192)
(1)求证:平面
平面EFD;
(2)求点
到平面
的距离.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0585b6c0f156eecf9662b9846d4eb693.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/93edc7bb513f40a89173121c8570cd65.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2f1b3863faf06a45b45ec3b0759c27a6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/326e8588bec54c0fb13bee6991519410.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3cf9b288c48c73463a2f214f02b6952a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3b3ec77f73bff82246c29ffb16dd4875.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/6/86d4b6bb-f892-4412-9cbb-c53216c52605.png?resizew=192)
(1)求证:平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/897c7b6907b4fd08cfacb36b7b993f97.png)
(2)求点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ebce46aeb97373353179e5669365fa4a.png)
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【推荐2】在四棱锥
中,
为等边三角形,
,
,点
为
的中点.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/28/4c468772-4545-427d-80f7-0acc2356e067.png?resizew=198)
(1)求证:
平面
;
(2)已知平面
平面
,求二面角
的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0585b6c0f156eecf9662b9846d4eb693.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/661ff55b5ebbadfb600989af3cfce2fd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/32450995497b9e341be832e9efad3114.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d4ad161a2674d823247f0d8236cae1d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48f3c9abbd78e9a6840ee5f30381daac.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/28/4c468772-4545-427d-80f7-0acc2356e067.png?resizew=198)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7175df06e33cad4e6bbc3f2f6b0a2986.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/852aabd89edffc1b94344ff3f1f31ccd.png)
(2)已知平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f04c222223dae9ef27d4c132534d9848.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7d5a2f5f4970ab8a1303523e23c8b24a.png)
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解题方法
【推荐1】如图,已知圆柱的上、下底面圆心分别为P,Q,
是圆柱的轴截面,正方形ABCD内接于下底面圆Q,AB=a,
.
(1)当a为何值时,点Q在平面PBC内的射影恰好是
的重心;
(2)在(1)条件下,求平面
与平面
所成二面角的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6ac61c24f99a4e466f1e2ea011893866.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/51d0fdc5a00ca0e857b89a7e1420df29.png)
(1)当a为何值时,点Q在平面PBC内的射影恰好是
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1c025ee3317be1099b7bf03a11e37ed4.png)
(2)在(1)条件下,求平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/852aabd89edffc1b94344ff3f1f31ccd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e7b7c83470489253394bd288d7c920df.png)
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【推荐2】如图,长方体
中,AB=4,AD=3,AA1=5,E,F分别在BB1,DD1上,且
,
![](https://img.xkw.com/dksih/QBM/editorImg/2022/10/13/0c2a9c98-3263-4c8e-bec7-3223daf865b7.png?resizew=212)
(1)求证:
平面
;
(2)求平面
与平面
的夹角的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e09725691ee7851f54c0dee86b2bf55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bc99486bf8b729aabccd7e7c1cecef36.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/10/13/0c2a9c98-3263-4c8e-bec7-3223daf865b7.png?resizew=212)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d26d8a9d64ad3c8cba28840b41ed7837.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b03428a8f91a5674cb8f54766c165f7e.png)
(2)求平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b03428a8f91a5674cb8f54766c165f7e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ab6bf42c7db96104456424e4d1be6c48.png)
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【推荐3】如图,AB是圆O的直径,点C是圆O上异于A,B的点,直线PC⊥平面ABC,E,F分别是PA,PC的中点.
(1)记平面BEF与平面ABC的交线为l,试判断直线l与平面PAC的位置关系,并加以证明;
(2)设(1)中的直线l与圆O的另一个交点为D,且点Q满足
.记直线PQ与平面ABC所成的角为θ,异面直线PQ与EF所成的角为α,二面角E﹣l﹣C的大小为β.求证:sinθ=sinαsinβ.
(1)记平面BEF与平面ABC的交线为l,试判断直线l与平面PAC的位置关系,并加以证明;
(2)设(1)中的直线l与圆O的另一个交点为D,且点Q满足
![](https://img.xkw.com/dksih/QBM/2014/5/22/1571735197384704/1571735202594816/STEM/fe360ef4630f4137844de7807a4b52b9.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/3/10/29f8132e-d52b-4bb3-be15-39727acee098.png?resizew=195)
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