积化和差:
f(x)=cos(∏/3+x)cos(∏/3-x)
= (1/2)·[cos(2π/3) + cos(2x)]
= (1/2)·[cos(2x) - (1/2)]
= (1/2)cos(2x) - (1/4)
∴f(x)最小正周期为:π
h(x) = f(x) - g(x)
= (1/2)[cos(2x) - sin(2x)]
= (1/2)·√2·cos[2x + (π/4)]
∴h(x)max = √2/2
此时,cos[2x + (π/4)] = 1
∴2x + (π/4) = 2kπ(k∈Z)
∴使h(x)取得最大值的x的集合为:{x∣x∈(kπ) - (π/8)},k∈Z