Function: elleta
Section: elliptic_curves
C-Name: elleta
Prototype: Gp
Help: elleta(w): w=[w1,w2], returns the vector [eta1,eta2] of quasi-periods
 attached to [w1,w2].
Doc: returns the quasi-periods $[\eta_{1},\eta_{2}]$
 attached to the lattice basis $\var{w} = [\omega_{1}, \omega_{2}]$.
 Alternatively, \var{w} can be an elliptic curve $E$ as output by
 \kbd{ellinit}, in which case, the quasi periods attached to the period
 lattice basis \kbd{$E$.omega} (namely, \kbd{$E$.eta}) are returned.
 \bprog
 ? elleta([1, I])
 %1 = [3.141592653589793238462643383, 9.424777960769379715387930149*I]
 @eprog
