θ 1 ( 2 z , q ) = 2 θ 1 ( z , q ) θ 2 ( z , q ) θ 3 ( z , q ) θ 4 ( z , q ) θ 2 ( 0 , q ) θ 3 ( 0 , q ) θ 4 ( 0 , q ) \theta_{1}\left(2z,q\right)=2\frac{\theta_{1}\left(z,q\right)\theta_{2}\left(z,q\right)\theta_{3}\left(z,q\right)\theta_{4}\left(z,q\right)}{\theta_{2}\left(0,q\right)\theta_{3}\left(0,q\right)\theta_{4}\left(0,q\right)}