Is there a sensible way to get the QED box produced by \qedhere aligned with the last line of the cases environment in a situation as in the examples below?
\documentclass{article} \usepackage{amsmath} \usepackage{amsthm} \begin{document} \begin{proof} This is a proof ending in a displayed \verb|cases| envirnoment, and without the \verb|\qedhere|. \[ \begin{cases} 1, & \text{in the first case;} \\ 2, & \text{in the second case;} \\ 3, & \text{in the third case,} \end{cases} \] \end{proof} \begin{proof} This is a proof ending in a displayed \verb|cases| envirnoment, and with the \verb|\qedhere| at the very end. \[ \begin{cases} 1, & \text{in the first case;} \\ 2, & \text{in the second case;} \\ 3, & \text{in the third case,} \end{cases} \qedhere \] \end{proof} \begin{proof} This is a proof ending in a displayed \verb|cases| envirnoment, and with the \verb|\qedhere| in the last line of that. \[ \begin{cases} 1, & \text{in the first case;} \\ 2, & \text{in the second case;} \\ 3, & \text{in the third case,} \qedhere \end{cases} \] \end{proof} \end{document} The same thing will happen in a proof ending in a displayed gathered environment, or any of the -ed variants.
casesenvironment is vertically centered with respect to the formula axis. If the cases are not equally important, they shouldn't be in acasesenvironment, I think.