θ2⁡(0,q)⁢θ3⁡(z,q)⁢θ4⁡(z,q)θ2⁡(z,q)=2⁢∑n=-∞∞(-1)n⁢qn2⁢ⅇⅈ⁢2⁢n⁢zq-n⁢ⅇ-ⅈ⁢z+qn⁢ⅇⅈ⁢z.