[Tex/LaTex] \qed or \qedhere at the end of split environment

amsmathamsthmhorizontal alignmentvertical alignment

While I was trying to improve my latest document with respect to its \qed symbols at the end of amsthm's proof environment i came across an interesting point. Assume the proof ends with some formula, that is finally representing the form the lemma/theorem proposes.

Something like

\documentclass{scrartcl}
\usepackage[fleqn]{amsmath}
\usepackage{amsthm,amstext,amsfonts,bm,amssymb}

\begin{document}
\begin{proof}
...
\begin{equation}
    \begin{split}
        A&= B \\
         &= C\\
         &= D&\qedhere
    \end{split}
\end{equation}
\end{proof}
\end{document}

While using \qedhere just in equation or align would put the symbol below any number (or at least to that side for euqation*), here the symbol is placed far to the left, even with using the additional column with &. Putting it after \end{split} would center it vertically with respect to the three columns, so my question is

How can I get the \qed symbol to the bottom right (text border) of an (equation-)split environment?

Where I would prefer a global solution for all splits where I mention \qedhere at the end.

Best Answer

the best approach in this particular case is to use align*, as that behaves well with \qedhere since each line is treated separately. (any of the multi-line options that treats lines separately should work equally well.)

\documentclass{scrartcl}
\usepackage[fleqn]{amsmath}
\usepackage{amsthm,amssymb}

\begin{document}
\begin{proof}
...
\begin{align*}
        A&= B \\
         &= C\\
         &= D \qedhere
\end{align*}
\end{proof}
\end{document}

this isn't always ideal -- cases, for example, will always force the tombstone to the center vertically -- but the request has been made often enough to place the tombstone on the last line, that it should be considered as a possible option. i am adding it to the formal list of requests.

as noted elsewhere, with flush left equations and equation numbers on the right, there is a built-in conflict. that is why ams document classes default to using equation numbers on the left.

Related Question