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在△ABC中,a、b、c分别为∠A、∠B、∠C的对边,三边a、b、c成等差数列,...
在△ABC中,a、b、c分别为∠A、∠B、∠C的对边,三边a、b、c成等差数列,且
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131025123721212973654/SYS201310251237212129736011_ST/0.png)
,则cosA-cosC的值为( )
A.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131025123721212973654/SYS201310251237212129736011_ST/1.png)
B.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131025123721212973654/SYS201310251237212129736011_ST/2.png)
C.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131025123721212973654/SYS201310251237212129736011_ST/3.png)
D.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131025123721212973654/SYS201310251237212129736011_ST/4.png)
考点分析:
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及到直线
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