Jacobi nd
From specialfunctionswiki
The $\mathrm{nd}$ function is defined by $$\mathrm{nd}(u)=\dfrac{1}{\mathrm{dn}(u)},$$ where $\mathrm{dn}$ is the Jacobi dn function.
Domain coloring of $\mathrm{nd}$ corresponding to $m=0.8$.
References
Special functions by Leon Hall