已知f(x)=sin(x+π/6)+sin(x-π/6)+acosx+b,(a,b∈R,且均为常数).(1)求函数f(x)的最小正周期;(2)若f(x)在区间[-π/3,0]上单调递增,且恰好能够取到f(x)的最小值2,试求a,b的值.
问题描述:
已知f(x)=sin(x+π/6)+sin(x-π/6)+acosx+b,(a,b∈R,且均为常数).(1)求函数f(x)的最小正周期;
(2)若f(x)在区间[-π/3,0]上单调递增,且恰好能够取到f(x)的最小值2,试求a,b的值.
答
f(x)=sin(x+π/6)+sin(x-π/6)+cosx+a
=2sinxcos(π/6)+cosx+a
=√3sinx+cosx+a
=2sin(x+π/6)+a,
1.最小正周期是2π.
2.x∈[-π/2,π/2],
x+π/6∈[-π/3,2π/3],
f(x)的最大值是2+a,最小值是a-√3,
依题意2+a+a-√3=a,
∴a=√3-2.
答
+sin(x-π/6) +acosx +b(a,b∈r,且均为常数)??? f(x)=sin(x+ π/6) +sin(x-π/6) +acosx +b(a,b∈r,且均为常数) =2sinx
答
f(x)=sin(x+ π/6) +sin(x-π/6) +acosx +b(a,b∈r,且均为常数)=2sinxcosπ/6+acosx+b=√3sinx+acosx+b=√(3+a^2)sin(x+θ)+b (sinθ=a/√(3+a^2),cosθ=√3/√(3+a^2),f(x)在区间[-π/3,0]上单调递增,且恰好能够...