θ3⁡(z|τ)=θ3⁡(0|τ)⁢∏n=1∞cos⁡((n-12)⁢π⁢τ+z)⁢cos⁡((n-12)⁢π⁢τ-z)cos2⁡((n-12)⁢π⁢τ),