f(x)=cos(2x+π/3)+sin*2(x-π)+a,
=cos2x*cosπ/3-sin2xsinπ/3+sin2x+a
=1/2*cos2x+(1-√3/2)sin2x+a
=bsin(2x+c)+a
所以
f(x)的最小正周期为:π