已知a,b,c分别为△ABC三个内角A,B,C的对边,
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102739136620995/SYS201311031027391366209016_ST/0.png)
(1)求A;
(2)若a=2,△ABC的面积为
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102739136620995/SYS201311031027391366209016_ST/1.png)
;求b,c.
考点分析:
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(1)若
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=3,tan(α-β)=2,求tan(β-2α)的值;
(2)已知sin(3π+θ)=
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,求
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+
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.
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在一个塔底的水平面上某点测得该塔顶的仰角为θ,由此点向塔底沿直线行走了30 m,测得塔顶的仰角为2θ,再向塔底前进10
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m,又测得塔顶的仰角为4θ,则塔的高度为
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对于函数f(x)=
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102739136620995/SYS201311031027391366209013_ST/0.png)
,给出下列四个命题:
①该函数是以π为最小正周期的周期函数;
②当且仅当x=π+kπ(k∈Z)时,该函数取得最小值-1;
③该函数的图象关于x=
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102739136620995/SYS201311031027391366209013_ST/1.png)
+2kπ(k∈Z)对称;
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![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103102739136620995/SYS201311031027391366209013_ST/2.png)
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其中正确命题的序号是
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sin
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图象上,相邻的一个最大值点与一个最小值点恰好在x
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