Revision history [back]

The division polynomial does not depend on the base field so it would be more efficient to compute it from the original E rather than its base change to QQbar. You can always find the roots of the polynomial in QQbar later. It is also strange that you first defined the curve over CC since it has rational coefficients, but we do not know what you were planning to do.

Once you have a polynomial with coefficients in QQ you can scale it how you like, so this is not really a question about elliptic curves.