Entire $f$ and $g$ constant if $e^{f(z)}+e^{g(z)}=1$

Solution 1:

I take it

one semester of graduate complex analysis

means you have heard of Picard's so-called "little" theorem.

The functions $e^{f(z)}$ and $e^{g(z)}$ are entire, and omit two values, hence they are constant. That immediately implies that $f$ and $g$ are constant.