23 Weierstrass Elliptic and Modular FunctionsWeierstrass Elliptic Functions

§23.7 Quarter Periods

23.7.1 ℘⁡(12⁢ω1) =e1⁡+(e1⁡−e3⁡)⁢(e1⁡−e2⁡)=e1⁡+ω1−2⁢(K⁡(k))2⁢k′,
23.7.2 ℘⁡(12⁢ω2) =e2⁡−i⁢(e1⁡−e2⁡)⁢(e2⁡−e3⁡)=e2⁡−i⁢ω1−2⁢(K⁡(k))2⁢k⁢k′,
23.7.3 ℘⁡(12⁢ω3) =e3⁡−(e1⁡−e3⁡)⁢(e2⁡−e3⁡)=e3⁡−ω1−2⁢(K⁡(k))2⁢k,

where k,k′ and the square roots are real and positive when the lattice is rectangular; otherwise they are determined by continuity from the rectangular case.