In this paper, an example is given, through which we have arrived at the following conclusion: the convergence radius of the first order approximate Tc series solutionfor μ*=0 is determined neither by nor by zph=-∫0(ωph)dωg(ω)dω(ω2)/(ωph2-ω2) nor by zph=∫0(ωph)dωg(ω)dω(ω2)/(ωph2+ω2).