Discriminant-ratio coordinate on X0 2
= Discriminant-ratio coordinate on X0 2
{title2=$t=\Delta(\tau)/\Delta(2\tau)$}
The ratio of <modular discriminants> has weight zero and level $\Gamma_0(2)$. It has one <simple pole> at infinity and one simple zero at the zero <modular cusp>, with no zeros or <poles> in the half-plane. It is a spherical coordinate by the <single-pole criterion for a spherical coordinate>. The <Klein j-invariant> is $(t+256)^3/t^2$, with $t(e^{2\pi i/3})=-256$.