f(x)的最小正周期是T=2π/(π/3)=6.
f(1)=√3/2
f(2)=√3/2
f(3)=0
f(4)=-√3/2
f(5)=-√3/2
f(6)=0
f(1)+f(2)+f(3)+f(4)+f(5)+f(6)=0
f(1)+f(2)+f(3)+…+f(2003)=f(1999)+f(2000)+f(2001)+f(2002)+f(2003)=0