1f(x)=sin方x+2倍根三sin(x+π4)cos(x-π4)-cos方x-根号三
1.f(x)=sin方x+2倍根三sin(x+π/4)cos(x-π/4)-cos方x-根号三 求最小正周期合单减区间
解:
,,
22f(x),sinx,23sin(x,)cos(x,),cosx,344,,22,(sinx,cosx),23sin(x,)cos(x,),344
2222,,cos2x,23(cosx,sinx)(cosx,sinx),3 2222,3sin2x,cox2x
,,2sin(2x,)6
T,,
3,,单调减区间带入公式即可。 [2k,,2k,],,22
2.f(x)=cos方x-sin方x+2倍根三sinxcosx+1 求最最小正周期及最小值
解:
22f(x),cosx,sinx,23sinxcosx,1
,,cos2x,3sin2x,1,,(3sin2x,cox2x),1,,2sin(2x,),1 6T,,
最小值-1
3.q=2,s99=56,a3+a6+...........+a99=?
解:
99a(1,q)561q,2,S,56,,56,a,991991,22,1 99299a(1,2)a2(1,2)31a,a,...,a,,,323699331,21,2
4.两等差数列满足a1+a2+.......+an/b1+b2+............+bn=7n+2/n+3,a5/b5=?
a,a,...,a7n,212nS,T,{a},{b},设数列的前n项和分别为,则有: nnnnb,b,...,bn,312n
9()a,a19
2SSa,aaa7272n,n1019552 ,,,,,,,9()b,b3213Tn,Tb,bbb19n101955
2
5.ap+q=ap+aq,a2=-6,p,q属于N正,a10=?
a,,6,a,a,a,,9,a,a,a,,12,a,...,a,,30 23124226106.等差数列{an}有2n+1项,其奇数项的和与偶数项的和值比为, 奇数项为n+1,偶数项为n
naa(,1)(,)12n,1
SSn,1奇奇2 aaaa?,,,,,,?,12n,122nnaa(,)SSn22n偶偶
2
.7等差数列{an}d不等于0,a1=9d,若ak是a1与a2k的等比中项,则k等于? 22a,aa,[a,(k,1)d],a[a,(2k,1)d],将a1=9d代入解方程即可。 k12k111