如圖:
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824011217691556.png)
中,E是AD中點,BE∩AC=F,
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824011217707654.png)
,求
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824011217723323.png)
的值.
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/201408240112177541647.png)
試題分析:設(shè)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824011217801577.png)
(2分)
則
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/201408240112178161085.png)
又
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824011217832998.png)
=
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/201408240112178471248.png)
(6分)
∴
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/201408240112178631122.png)
∴
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824011217769495.png)
(8分)
點評:解答此類問題的關(guān)鍵是掌握平面向量的運算法則及向量相等的概念,屬基礎(chǔ)題
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