如图,在空间四边形OABC中,M,G分别是BC,AM的中点,设
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101224251021178948/SYS201311012242510211789021_ST/0.png)
,
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101224251021178948/SYS201311012242510211789021_ST/1.png)
,
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101224251021178948/SYS201311012242510211789021_ST/2.png)
.
(1)用基底
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101224251021178948/SYS201311012242510211789021_ST/3.png)
表示向量
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101224251021178948/SYS201311012242510211789021_ST/4.png)
;
(2)若
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101224251021178948/SYS201311012242510211789021_ST/5.png)
,且
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101224251021178948/SYS201311012242510211789021_ST/6.png)
与
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101224251021178948/SYS201311012242510211789021_ST/7.png)
、
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101224251021178948/SYS201311012242510211789021_ST/8.png)
夹角的余弦值均为
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101224251021178948/SYS201311012242510211789021_ST/9.png)
,
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101224251021178948/SYS201311012242510211789021_ST/10.png)
与
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101224251021178948/SYS201311012242510211789021_ST/11.png)
夹角为60°,求
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101224251021178948/SYS201311012242510211789021_ST/12.png)
.
考点分析:
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![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101224251021178948/SYS201311012242510211789016_ST/0.png)
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