如图,在四棱锥
中,底面
是正方形,![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5a1b49f64e0065edad868b25e9fcada3.png)
,
,
是棱
的中点.
//平面
;
(2)再从条件①、条件②这两个条件中选择一个作为已知,求平面
与平面
夹角的余弦值.
条件①:平面
平面
;
条件②:
.
注:如果选择条件①和条件②分别解答,按第一个解答计分.
![](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/5a1b49f64e0065edad868b25e9fcada3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1ba172e1d3af3079d5d8fcb3791d6484.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bd33764ff4efddfe11a98a609753715c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48f3c9abbd78e9a6840ee5f30381daac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/34be4e71cabf458f17a6cd7f24bc70af.png)
(2)再从条件①、条件②这两个条件中选择一个作为已知,求平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/34be4e71cabf458f17a6cd7f24bc70af.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
条件①:平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/93edc7bb513f40a89173121c8570cd65.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
条件②:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f9425630dcfe5a824c44904d4f71e13.png)
注:如果选择条件①和条件②分别解答,按第一个解答计分.
更新时间:2023-11-02 17:57:43
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【推荐1】P为正方形ABCD所在平面外一点,E,F,G分别为PD,AB,DC的中点,如图.求证:
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【推荐2】在多面体
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(2)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9f4c3f9dd5d0343597a7f58a1989b537.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/10fc7991ea17d54ff5f4445ac5699463.png)
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(2)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d26d8a9d64ad3c8cba28840b41ed7837.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fae7f4612c548b1f72a964ddb291cd2e.png)
(3)若
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解答题-证明题
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适中
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的底面
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,
,
、
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、
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![](https://img.xkw.com/dksih/QBM/2011/4/8/1570112387612672/1570112393060352/STEM/f690ffb5-f37c-476d-8168-524054a1277f.png?resizew=212)
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;
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的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/faeb97acf19bd3b2c6c77c2814df4d2f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bc9c9cfa597b444b5c9dbae7a825a695.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cfef4f8fc97c348dd612917960736fce.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fcd0ced286a0fbc7e4862f8147264277.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/defa5b53043ae802bb1af7d14374406d.png)
![](https://img.xkw.com/dksih/QBM/2011/4/8/1570112387612672/1570112393060352/STEM/f690ffb5-f37c-476d-8168-524054a1277f.png?resizew=212)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b57e0d440e8ccf29fe5f9b3605ad27ca.png)
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解答题-问答题
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适中
(0.65)
【推荐2】在三棱柱
中,
,
为
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底面
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在线段
上,且
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![](https://img.xkw.com/dksih/QBM/editorImg/2023/1/6/5e7d6fe2-fb5d-4a06-8ce9-3f077021029f.png?resizew=246)
(1)证明:
;
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42d3a82b8e587ee890467835bc4e854c.png)
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![](https://img.xkw.com/dksih/QBM/editorImg/2023/1/6/5e7d6fe2-fb5d-4a06-8ce9-3f077021029f.png?resizew=246)
(1)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/71f03f92620e2663e49cc98d2303908c.png)
(2)若
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ce78c975ff520557d080e7fbae76d01c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e16368cd7cd132082fc9d6dbf6266bc1.png)
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