已知a、b、c分别是△ABC的三个内角A、B、C所对的边;
(1)若△ABC面积
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103100647184254982/SYS201311031006471842549017_ST/0.png)
,求a、b的值;
(2)若a=ccosB且b=csinA,试判断△ABC的形状.
考点分析:
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已知等差数列{a
n}中,a
3+a
6=17,a
1a
8=-38且a
1<a
8.
(1)求{a
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(2)调整数列{a
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1、a
2、a
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已知下列五个命题
①若b
2=ac,则a,b,c成等比数列;
②若{a
n}是等比数列,且
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,则r=-1;
③若数列{b
n}的前n项和S
n=n
2+2n+1,则数列{b
n}从第二项起成等差数列;
④已知
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,则xy的最小值是6.
⑤在△ABC中,若A>B,则sinA>sinB.
请把正确的命题的题号都填在后面的横线上
.
查看答案
已知数列{a
n}:
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103100647184254982/SYS201311031006471842549014_ST/0.png)
,
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+
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,
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+
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+
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,
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+
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103100647184254982/SYS201311031006471842549014_ST/7.png)
+
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103100647184254982/SYS201311031006471842549014_ST/8.png)
+
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,…,那么数列b
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![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103100647184254982/SYS201311031006471842549014_ST/10.png)
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的最小值为
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的值为
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