在正方體
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824025837510787.png)
中,
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824025837525320.png)
是
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824025837541387.png)
的中點,則異面直線
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824025837557439.png)
與
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824025837572447.png)
所成角的大小是( )
試題分析:在正方體
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824025837510787.png)
中,容易得到
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824025837650464.png)
平面
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824025837666580.png)
,又因為
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824025837681494.png)
平面
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824025837666580.png)
,故得到
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824025837713646.png)
.
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824025837728168.png)
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