How to tell where parentheses go in functional notation? The professor gave us a function $f(z) = \ln r + i \theta$ (this is for a complex analysis class). He doesn't like answering students' questions and there's no assigned textbook so I don't know where to look up such a function. How can I tell where the parentheses are supposed to go for this equation?

In addition to syntactic answers already discussed, you can think a little about which makes the most sense in context.  For a complex analysis class, $f(z) = \ln(r) + i\theta$ is a common function to encounter.  If $z$ is a complex number with modulus $r$ and principal argument $\theta$, then $f(z)$ is the principal branch of the complex logarithm, a function which is used all the time.  On the other hand, $f(z) = \ln(r + i\theta)$ doesn't seem to be a particularly useful function.
