Bi⁡(z)+ⅇ-2⁢π⁢ⅈ/3⁢Bi⁡(z⁢ⅇ-2⁢π⁢ⅈ/3)+ⅇ2⁢π⁢ⅈ/3⁢Bi⁡(z⁢ⅇ2⁢π⁢ⅈ/3)=0.