Period lattice of the Jacobi elliptic sine
= Period lattice of the Jacobi elliptic sine
For real $0<k<1$, the <period lattice> of $\operatorname{sn}(u,k)$ is generated by
$$
4K(k)
\quad\hbox{and}\quad
2iK'(k).
$$
The periods arise by composing the <monodromy reflection at a square-root branch point>[monodromy reflections] of its inverse <elliptic integral of the first kind>.