limk1𝐸𝑐νm(z,k2)𝐸𝑐νm(0,k2)=limk1𝐸𝑠νm+1(z,k2)𝐸𝑠νm+1(0,k2)=1(coshz)μF(12μ12ν,12μ+12ν+1212;tanh2z),