满分5 >
高中数学试题 >
等差数列{an}的前n项和为Sn,若a2+a8+a11=30,那么S13值的是(...
等差数列{an}的前n项和为Sn,若a2+a8+a11=30,那么S13值的是( )
A.130
B.65
C.70
D.以上都不对
考点分析:
相关试题推荐
已知
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183239622766815/SYS201310241832396227668004_ST/0.png)
的最小正周期为π,要得到y=f(x)的图象,只需把y=sinωx的图象( )
A.向左平移
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183239622766815/SYS201310241832396227668004_ST/1.png)
个单位
B.向右平移
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183239622766815/SYS201310241832396227668004_ST/2.png)
个单位
C.向左平移
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183239622766815/SYS201310241832396227668004_ST/3.png)
个单位
D.向右平移
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183239622766815/SYS201310241832396227668004_ST/4.png)
个单位
查看答案
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183239622766815/SYS201310241832396227668003_ST/images0.png)
如图,在半径为R的圆内随机撒一粒黄豆,它落在阴影部分内接正三角形上的概率是( )
A.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183239622766815/SYS201310241832396227668003_ST/0.png)
B.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183239622766815/SYS201310241832396227668003_ST/1.png)
C.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183239622766815/SYS201310241832396227668003_ST/2.png)
D.
查看答案
若
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183239622766815/SYS201310241832396227668002_ST/0.png)
是夹角为
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183239622766815/SYS201310241832396227668002_ST/1.png)
的单位向量,且
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183239622766815/SYS201310241832396227668002_ST/2.png)
,
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183239622766815/SYS201310241832396227668002_ST/3.png)
,则
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183239622766815/SYS201310241832396227668002_ST/4.png)
=( )
A.1
B.-4
C.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183239622766815/SYS201310241832396227668002_ST/5.png)
D.
查看答案
设z=1+i(i是虚数单位),则
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183239622766815/SYS201310241832396227668001_ST/0.png)
=( )
A.-1-i
B.-1+i
C.1-i
D.1+i
查看答案
已知集合M={x|x
2-4x+3<0},N={x|2x+1<5},则M∪N=( )
A.{x|x>3}
B.{x|x>2}
C.{x|x<3}
D.{x|x<2}
查看答案