W⁡(a,x)=k/2⁢ⅇ14⁢π⁢a⁢(ⅇⅈ⁢ρ⁢U⁡(ⅈ⁢a,x⁢ⅇ-π⁢ⅈ/4)+ⅇ-ⅈ⁢ρ⁢U⁡(-ⅈ⁢a,x⁢ⅇπ⁢ⅈ/4)),