在△ABC中,三内角A,B,C的对边分别为a,b,c且满足(2b-c)cosA=acosC
(Ⅰ)求角A的大小;
(Ⅱ)若|
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103095951756240527/SYS201311030959517562405016_ST/0.png)
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![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103095951756240527/SYS201311030959517562405016_ST/1.png)
|=1,求△ABC周长l的取值范围.
考点分析:
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(选修4-4:坐标系与参数方程)
直线l的极坐标方程为C:ρcos(θ-
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)=3
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103095951756240527/SYS201311030959517562405015_ST/1.png)
,圆C:
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103095951756240527/SYS201311030959517562405015_ST/2.png)
(θ为参数)上的点到直线l的距离值为d,则d的最大值为
.
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![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103095951756240527/SYS201311030959517562405014_ST/images0.png)
如图,圆O的直径AB=6,C为圆周上一点,BC=3,过C作圆的切线l,过A作l的垂线AD,垂足为D,则线段CD的长为
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定义
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103095951756240527/SYS201311030959517562405013_ST/0.png)
,设实数x,y满足约束条件
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103095951756240527/SYS201311030959517562405013_ST/1.png)
,z=max{4x+y,3x-y},则z的取值范围是
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在计算“1×2+2×3+…+n(n+1)”时,有如下方法:
先改写第k项:k(k+1)=
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103095951756240527/SYS201311030959517562405012_ST/0.png)
[k(k+1)(k+2)-(k-1)k(K+1)],
由此得:1×2=
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103095951756240527/SYS201311030959517562405012_ST/1.png)
(1×2×3-0×1×2),
2×3=
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103095951756240527/SYS201311030959517562405012_ST/2.png)
(2×3×4-1×2×3),…,
n(n+1)=
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103095951756240527/SYS201311030959517562405012_ST/3.png)
[n(n+1)(n+2)-(n-1)n(n+1)],
相加得:1×2+2×3+…+n(n+1)=
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103095951756240527/SYS201311030959517562405012_ST/4.png)
(n+1)(n+2).
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![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103095951756240527/SYS201311030959517562405011_ST/images0.png)
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