# \qed vertical alignment in Beamer

I am using beamer for some presentation and when I end the proof with a multi-line equation, I cannot set the positition the \qed symbol at the end of the last equation line.

\documentclass[10pt]{beamer}

\usetheme{Warsaw}
\usecolortheme{seahorse}

\renewcommand{\qedsymbol}{{\usebeamercolor[fg]{structure}$\blacksquare$}}

\begin{document}

\begin{frame}

\begin{block}{\proofname}
Some text here
$$\begin{cases} 1\\ 2\\ 3\\ 4. \end{cases}\notag$$
\hfill\qedsymbol
\end{block}

\end{frame}

\end{document}


This gives me the following output

but I need the following.

Here is an quick and dirty way of doing it:

\documentclass[10pt]{beamer}
\usetheme{Warsaw}
\usecolortheme{seahorse}

\renewcommand{\qedsymbol}{\raisebox{\dimexpr\belowdisplayskip+\lineskip\relax}[0pt]{\usebeamercolor[fg]{structure}$\blacksquare$}\vspace{-\belowdisplayskip}}

\begin{document}

\begin{frame}
\begin{block}{\proofname}
Some text here
$$\begin{cases} 1\\ 2\\ 3\\ 4. \end{cases}\notag$$
\hfill\qedsymbol
\end{block}
\end{frame}

\end{document}


An extra space (seems 5pt, not sure why) will be inserted when the equation is too long so further adjustment is needed.

You might do like this, but I'm not sure you really need an end of proof symbol.

\documentclass[10pt]{beamer}

\usetheme{Warsaw}
\usecolortheme{seahorse}

\renewcommand{\qedsymbol}{{\usebeamercolor[fg]{structure}$\blacksquare$}}

\begin{document}

\begin{frame}

\begin{block}{\proofname}\pushQED{\qed}
Some text here
\begin{equation*}
\begin{gathered}[b]
\begin{cases}
1\\
2\\
3\\
4.
\end{cases}\\[-1.2\normalbaselineskip]
\mathstrut
\end{gathered}\qedhere
\end{equation*}
\popQED\end{block}

\end{frame}