You have E.lift_x(x0) which gives a point with x-coord x0 if there is one (else raises an error), or E.lift_x(x0,all=True) which gives a list of 0, 1 or 2 points with x-coord x0, or E.is_x_coord(x0).
JEC 2008/9/3 Maike <[EMAIL PROTECTED]>: > > John, > > Hello again :-) While you're working on more elliptic curves stuff, > what I could use is the following: > I'd like to define points on curves by just providing the x-coordinate > (and maybe an indicator of which of the possible two y-coordinates I > want). When I do something like > > E = EllipticCurve(RR,[a,b]) > P = E([xP,sqrt(xP^3+a*xP+b)]) > > it doesn't always work. > > Or is there a way of doing this already? > > Maike > > > --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-support URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
