满分5 >
高中数学试题 >
设{an}是公差为-2的等差数列,若a1+a4+a7+…+a97=50,则a3+...
设{an}是公差为-2的等差数列,若a1+a4+a7+…+a97=50,则a3+a6+a9+…+a99等于( )
A.82
B.-82
C.132
D.-132
考点分析:
相关试题推荐
在等比数列{a
n}中,已知
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131023214059458666838/SYS201310232140594586668000_ST/0.png)
,则n为( )
A.2
B.3
C.4
D.5
查看答案
设关于x的方程sinx+
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131023214059458663603/SYS201310232140594586636017_ST/0.png)
cosx+a=0在(0,2π)内有相异二解α、β.
(1)求α的取值范围.(2)求tan(α+β)的值.
查看答案
在△ABC中,sinA+cosA=
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131023214059458663603/SYS201310232140594586636016_ST/0.png)
,AC=2,AB=3,求tanA的值和△ABC的面积.
查看答案
已知sin(
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131023214059458663603/SYS201310232140594586636015_ST/0.png)
+2α)•sin(
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131023214059458663603/SYS201310232140594586636015_ST/1.png)
-2α)=
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131023214059458663603/SYS201310232140594586636015_ST/2.png)
,α∈(
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131023214059458663603/SYS201310232140594586636015_ST/3.png)
,
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131023214059458663603/SYS201310232140594586636015_ST/4.png)
),求2sin
2α+tanα-cotα-1的值.
查看答案
已知sin(α+β)=-
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131023214059458663603/SYS201310232140594586636014_ST/0.png)
,cos(α-β)=
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131023214059458663603/SYS201310232140594586636014_ST/1.png)
,且
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131023214059458663603/SYS201310232140594586636014_ST/2.png)
<β<α<
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131023214059458663603/SYS201310232140594586636014_ST/3.png)
,求sin2α.
查看答案