Function: rnfelttrace
Section: number_fields
C-Name: rnfelttrace
Prototype: GG
Help: rnfelttrace(rnf,x): returns the relative trace Tr_{L/K}(x), as an element
 of K.
Doc: $\var{rnf}$ being a relative number field extension $L/K$ as output by
 \kbd{rnfinit} and $x$ being an element of $L$, returns the relative trace
 $Tr_{L/K}(x)$ as an element of $K$.
 \bprog
 ? K = nfinit(y^2+1); L = rnfinit(K, x^2-y);
 ? rnfelttrace(L, Mod(x, L.pol))
 %2 = 0
 ? rnfelttrace(L, 2)
 %3 = 4
 @eprog

