Hi, Maxima says (C39) 1/sqrt(x)-sqrt(1/x); (D39) 0 but (C40) 1/sqrt(-1)-sqrt(1/(-1)); (D40) -2*%I This is inconsistent! How is sqrt(x) treated in Maxima? I.e. is it multi valued (then it should be treated as a set) or is it single valued (e.g. the complex number z with Re(z)>=0 and z^2=x)? Felix