满分5 >
高中数学试题 >
如果等差数列{an}中,a3+a4+a5=12,那么a1+a2+…+a7=( )...
如果等差数列{an}中,a3+a4+a5=12,那么a1+a2+…+a7=( )
A.14
B.21
C.28
D.35
考点分析:
相关试题推荐
已知函数
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625009_ST/0.png)
;则y=f(x)的图象大致为( )
A.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625009_ST/images1.png)
B.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625009_ST/images2.png)
C.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625009_ST/images3.png)
D.
查看答案
已知
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625008_ST/0.png)
与
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625008_ST/1.png)
均为单位向量,其夹角为θ,有下列四个命题P
1:|
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625008_ST/2.png)
+
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625008_ST/3.png)
|>1⇔θ∈[0,
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625008_ST/4.png)
);P
2:|
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625008_ST/5.png)
+
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625008_ST/6.png)
|>1⇔θ∈(
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625008_ST/7.png)
,π];P
3:|
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625008_ST/8.png)
-
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625008_ST/9.png)
|>1⇔θ∈[0,
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625008_ST/10.png)
);P
4:|
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625008_ST/11.png)
-
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625008_ST/12.png)
|>1⇔θ∈(
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625008_ST/13.png)
,π];其中的真命题是( )
A.P
1,P
4B.P
1,P
3C.P
2,P
3D.P
2,P
4
查看答案
由曲线y=
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625007_ST/0.png)
,直线y=x-2及y轴所围成的图形的面积为( )
A.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625007_ST/1.png)
B.4
C.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625007_ST/2.png)
D.6
查看答案
设三棱柱的侧棱垂直于底面,所有棱长都为a,顶点都在一个球面上,则该球的表面积为( )
A.πa
2B.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625006_ST/0.png)
C.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625006_ST/1.png)
D.C
1
查看答案
若
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625005_ST/0.png)
,α是第三象限的角,则
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625005_ST/1.png)
=( )
A.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625005_ST/2.png)
B.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101017105462565/SYS201311031010171054625005_ST/3.png)
C.2
D.-2
查看答案