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已知两个单位向量,的夹角为,若向量=-2,=3+4,则=( ) A.-6 B. ...
已知两个单位向量
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102526802294146/SYS201311031025268022941003_ST/0.png)
,
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102526802294146/SYS201311031025268022941003_ST/1.png)
的夹角为
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102526802294146/SYS201311031025268022941003_ST/2.png)
,若向量
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102526802294146/SYS201311031025268022941003_ST/3.png)
=
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102526802294146/SYS201311031025268022941003_ST/4.png)
-2
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102526802294146/SYS201311031025268022941003_ST/5.png)
,
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102526802294146/SYS201311031025268022941003_ST/6.png)
=3
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102526802294146/SYS201311031025268022941003_ST/7.png)
+4
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102526802294146/SYS201311031025268022941003_ST/8.png)
,则
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102526802294146/SYS201311031025268022941003_ST/9.png)
=( )
A.-6
B.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102526802294146/SYS201311031025268022941003_ST/10.png)
C.-4
D.-5
考点分析:
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![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102526801605790/SYS201311031025268016057019_ST/0.png)
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![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102526801605790/SYS201311031025268016057019_ST/2.png)
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