I have this function.
SetAttributes[zf,HoldAllComplete]; zf[x_] := If[Denominator[Unevaluated[x]] == 0, Numerator[Unevaluated[x]], Numerator[Unevaluated[x]]];
It is supposed to just return the numerator anytime the denominator is 0.
It works fine when the denominator is literally 0, but it fails when there are functions/variables, such as when
Cos[x] == 0.
How would I go about evaluating the denominator separately, then if that equals zero, drop the denominator, and evaluate the numerator only without evaluating the entire fraction?
Basically my question is how do I make
1/Cos[-(3*Pi)/2 + z]or of
1/(Cos[-(3*Pi)/2] + z)for $z\to 0$. But more information is needed to decide what you really need. $\endgroup$