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复数z=(2+i)i的虚部是( ) A.2 B.-2 C.2i D.-2i
复数z=(2+i)i的虚部是( )
A.2
B.-2
C.2i
D.-2i
考点分析:
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已知向量
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102344469262154/SYS201311031023444692621014_ST/0.png)
=(cosx,sinx),
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102344469262154/SYS201311031023444692621014_ST/1.png)
=(-cosx,cosx),
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=(-1,0).
(Ⅰ)若
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102344469262154/SYS201311031023444692621014_ST/3.png)
,求向量
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、
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的夹角;
(Ⅱ)当
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102344469262154/SYS201311031023444692621014_ST/6.png)
时,求函数
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102344469262154/SYS201311031023444692621014_ST/7.png)
的最大值.
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已知
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102344469262154/SYS201311031023444692621013_ST/0.png)
,
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102344469262154/SYS201311031023444692621013_ST/1.png)
是非零向量,
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102344469262154/SYS201311031023444692621013_ST/2.png)
与
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102344469262154/SYS201311031023444692621013_ST/3.png)
的夹角为θ,当
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(t∈R)的模取得最小值时.
(1)求t的值;
(2)若
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与
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同向共线,求证:
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.
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如图△OAB,设
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,若
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,
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,设AN与BM交于P,用
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来表示向量
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.
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在△ABC中,O为中线AM上一个动点,若AM=2,则
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的最小值是
.
查看答案
已知
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=(3,-1),
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=(1,2),
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102344469262154/SYS201311031023444692621010_ST/2.png)
=
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,则
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的坐标是
.
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