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如果等腰三角形的周长是底边长的5倍,那么它的顶角的余弦值为( ) A. B. C...
如果等腰三角形的周长是底边长的5倍,那么它的顶角的余弦值为( )
A.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102756334365121/SYS201311031027563343651005_ST/0.png)
B.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102756334365121/SYS201311031027563343651005_ST/1.png)
C.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102756334365121/SYS201311031027563343651005_ST/2.png)
D.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102756334365121/SYS201311031027563343651005_ST/3.png)
考点分析:
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B.-
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若
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102756334365121/SYS201311031027563343651002_ST/0.png)
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或
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4
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