如图,在三棱锥
中,平面
平面
是等边三角形,
,
分别是
的中点.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/18/a03837f5-597f-4633-865b-13e1fe57a0df.png?resizew=145)
(1)求证
;
(2)求二面角
的正弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63397cda22cb1fad59cf966dfb588643.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6d077f6da8b2c00b152d4679aa2ed7f7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7eafd509d9cc5c7618aee2967105364b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5fc060366fff50795ac657153653117e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e7490886e2807c7b8a4fa57d99c4dc3a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f8d25599d59d4b2f54f8537108fdcc41.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/18/a03837f5-597f-4633-865b-13e1fe57a0df.png?resizew=145)
(1)求证
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d7e56367ffbcd363e8734d9314750b5.png)
(2)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6f2edd3e5b926b9bb6e34ef4ada50914.png)
更新时间:2021-02-09 07:50:38
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解答题-证明题
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适中
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【推荐1】如图,四棱锥
中,底面
为平行四边形,
底面
,
是棱
的中点,且
,![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e45bcd8f6ede8cc2513ad41402f40086.png)
.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/29/9211a02f-8d15-464a-8fad-eca4b1486c10.png?resizew=226)
(1)求证:
平面
;
(2)棱
上是否存在一点
,使得直线
与平面
所成角的正弦值为
,若存在,求
的值;若不存在,说明理由.
![](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/ccd4fd4b7a4d6b8ca0c5827c055a9ce7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e0629ce42392a7fe9be21d25c39c3e64.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/98e624e6ee68b796f70f9d35e78a8aed.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e45bcd8f6ede8cc2513ad41402f40086.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0c1ac2e11788860424508ea9e80cf89d.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/29/9211a02f-8d15-464a-8fad-eca4b1486c10.png?resizew=226)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/97f30533da2e1d2a958dc906c37eba9d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0628681907ac8d7fdb94d8bc1b15feb9.png)
(2)棱
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54a5d7d3b6b63fe5c24c3907b7a8eaa3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/167d31eb8432b5c0364316e5048c23dd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/daf2f0df53aa68c9c334165034788166.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e64e76a4c1e5934f51cdca2ffbc8313f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c2d109733379365295b93c58769d2019.png)
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【推荐2】如图所示,在四棱柱
中,底面
是梯形,
,侧面
为菱形,
.
![](https://img.xkw.com/dksih/QBM/2020/8/10/2524927743574016/2527670660644864/STEM/5926af6ed9bc45b29d5195509423c3c6.png?resizew=425)
(1)求证:
;
(2)若
,点D在平面
上的射影恰为线段
的中点,求平面
与平面
所成锐二面角的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e09725691ee7851f54c0dee86b2bf55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/34e0a957a55460c72673c0f2ee90dbb3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ab3e0dba5705e1d749cfb21ebbb2ed93.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ae5a19e74dfd34b87b2f3e4d16c583cb.png)
![](https://img.xkw.com/dksih/QBM/2020/8/10/2524927743574016/2527670660644864/STEM/5926af6ed9bc45b29d5195509423c3c6.png?resizew=425)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b5b0bfe1e7a956345f7ed58a3b2faa70.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d11340b4efe070df4a9f00744fa8f310.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ab3e0dba5705e1d749cfb21ebbb2ed93.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e26d9636ad77369535852c6e4493446a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7b54387f870ae37f7951b253665d64f6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ab3e0dba5705e1d749cfb21ebbb2ed93.png)
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解答题-证明题
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适中
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【推荐1】在三棱锥
中,
,
,
.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/26/5fc91cde-4623-4c26-92bf-868e91b1a110.png?resizew=168)
(1)求证:平面
平面
;
(2)若点
满足
,求二面角
的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63397cda22cb1fad59cf966dfb588643.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d026b53da98365d1ad870639dd90ac4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/305a88d4e0249bd16d48eda01331d2d4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6a7279d0fcdc535933caa4d583386ad0.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/26/5fc91cde-4623-4c26-92bf-868e91b1a110.png?resizew=168)
(1)求证:平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e4aa9084b8fe0fe05c4388d1f835587b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
(2)若点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/19519e0da4fb9a9654bfe16a8c46a026.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/324a1792318a3528772781fac2b4d2e4.png)
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解题方法
【推荐2】如图,在四棱锥
中,
,
,
,
,
,
,
.
![](https://img.xkw.com/dksih/QBM/2021/4/16/2701253204541440/2702662287712256/STEM/fb43fee6-8731-4542-acb2-eead5aaa01dc.png?resizew=167)
(1)证明;平面
平面
;
(2)若
,点
在
上,且
,求二面角
的大小.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/80c753cb1eb73fd8d136d00462970797.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4151e948feebdf7b91fbe739feafa9bc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f571396be1aa4a8914a66f7d7abd6381.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d7ee81b6066188abee9d167b6c7f3f71.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f09b595ff4d01d4d117f40d16a8f6e1a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ef0402dd5ae3db10281f9f1e11738bcb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0c14a66ed4bd66df65bc42c4ac1ed15c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49f6d31c549cd8cd285bce829d3bd8ef.png)
![](https://img.xkw.com/dksih/QBM/2021/4/16/2701253204541440/2702662287712256/STEM/fb43fee6-8731-4542-acb2-eead5aaa01dc.png?resizew=167)
(1)证明;平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/39282bdf319f30d7bc261e2e3ab3b1e4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c09afc70f448545336304333d5b5658b.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/57d0c097978d2c04110e53b2d24daa82.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1fc56c77464a17a1e97b568762a3e2c6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/db568791ce3434783ccb0d6c36d78092.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1ae628604c47725bb01e22dff5dca8e5.png)
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【推荐3】如图,在三棱柱
中,D是
的中点,E是CD的中点,点F在
上,且
.
平面
;
(2)若
平面ABC,
,
,求平面DEF与平面
夹角的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42d3a82b8e587ee890467835bc4e854c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2777840758e70e7dbbc18cef8f3d6d2b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e26d9636ad77369535852c6e4493446a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42a9b4db32c930bc04606ddc9f23bbc0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/06222ee533c2484ab25321a6abbf98cb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5845ccc0d735dc14c92a8926d9b1def6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/36c4559d27e3905980d1a4f1856f07de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2af2626608f61a4cfbb86494bd6df0e2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b1f68454096da710903e9693c7f2015.png)
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