I found out that doing
NdivV[z_] := z qdivV'[z]
is different from
NdivV[z_] := z D[qdivV[z],z]
Because the latter will give me a result that when i try to evaluate yields the General::ivar error saying that "A product cannot be used as a variable" Why can't it be so?
It would be a great surprise if N0[z_] := z*D[-Log[1 - z], z] would work fine. Try e.g. N0[1]!
If N0[1] is evaluated, the parameter: z is replaced by 1 resulting in:
1*D[-Log[1-1],1]
what is garbage.
Also, to my surprise
N0[z_] := z*D[-Log[1 - z], z]
works fine!
The ' stands for the function Derivative rather than the function D.
See the documentation: tutorial/TheRepresentationOfDerivatives
