relative number field subfield method -- unclear documentation #5392
Description
Consider
sage: R.<a> = NumberField(x^4 - 2*x^2 - 1)
sage: S.<i> = R.extension(x^2 + 1)
sage: S.subfield(a + i/a)
The S.subfield method documentation says that it constructs QQ(alpha), but this is false, I think it constructs R(alpha). In the above example, S.subfield(a + i/a) returns a number field of degree 8 over Q, whereas a + i/a has degree 4 over QQ (the minimal polynomial is x^4 - 4x^2 + 8).
Component: number fields
Keywords: sd51
Author: Alejandro Argaez
Reviewer: Michiel Kosters
Merged: sage-5.11.rc0
Issue created by migration from https://trac.sagemath.org/ticket/5392