(1)f(x)=1/2sin2xsina+(1+cos2x)/2•cosa-1/2cosa=1/2sin2xsina+1/2 cos2x cosa=1/2cos(2x-a),代入(π/6,1/2)得a=π/3.(2) y=g(x)= 1/2cos(4x-π/3),4x-π/3∈[-π/3,2π/3],最大值是1/2,最小值是-1/4....