名校
1 . 在三棱锥
中,
,
平面
,点M是棱
上的动点,点N是棱
上的动点,且
.
![](https://img.xkw.com/dksih/QBM/2024/1/30/3422378703052800/3432026374717440/STEM/d16a09eff99f4f52b2501b3b39b7caac.png?resizew=200)
(1)当
时,求证:
;
(2)当
的长最小时,求平面
与平面
夹角的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63397cda22cb1fad59cf966dfb588643.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/74375e1ba9d3a5d373479874b6634e96.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b5f1897a7e856b42f8cee0f286ad913d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bd33764ff4efddfe11a98a609753715c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bdc281ca213b922e5c4bddafd4ef08df.png)
![](https://img.xkw.com/dksih/QBM/2024/1/30/3422378703052800/3432026374717440/STEM/d16a09eff99f4f52b2501b3b39b7caac.png?resizew=200)
(1)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d94188fea61c347a150744709920d96e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/66fae8e33cd86fa8dab72704eaafe1ba.png)
(2)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411461db15ee8086332c531e086c40c7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1885efcff0b903e314057dd153578600.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/70db40c42655327adee01caedfc9d50c.png)
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2024-03-12更新
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393次组卷
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6卷引用:山东省安丘市青云学府2023届高三下学期一模数学试题