Hi there,
do you know of a function, which solves the Tietze for subgroups or converts elements from parentgroup to elements of subgroup and the other way round (if possible)? Neither of the commented codes work (but I hope it is clear what I want):
F.<a,b,c> = FreeGroup()
x=a*b/c
H=F.subgroup([a*b,b,b*c])
y=H.gens()[1]*H.gens()[0]
x in H
y in F
#F(y)
#F.coerce(y)
#H.coerce(x).Tietze()
#H(x)
I am using cocalc, if this is a version thing. I know something like that exists for quotient groups (s. http://doc.sagemath.org/html/en/reference/groups/sage/groups/finitely_presented.html )
In my use-case I have a free group F and an element x∈F in it. Now I want for a given list of generators (e.g. in above $[ab,b,bc])thexasawordofthesegenerators,henceIwouldliketoseexasanelementinHanduseTietze$.
Another solution to my problem would be to swap the generators, but I can't see a way to do that either?