Solid black box in the proof environment

Question

I am using

\documentclass[12pt]{article}

\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{amsthm}

\begin{document}

\begin{proof}
A = B
\end{proof}

\end{document}

and an empty square box will be added automatically at the end of the proof. I am wondering how to add a solid black box instead, in an automatic way.

Please add a minimal working example (MWE) that shows your document class and the relevant (theorem-related) packages. — lockstep, Feb 15 '13 at 17:37
\renewcommand{\qedsymbol}{\rule{1ex}{1ex}} put in the preamble, would it work? — yo', Feb 15 '13 at 17:40

score 64 · Accepted Answer · edited Apr 13 '17 at 12:35

The documentation of amsthm says:

A QED symbol, □, is automatically appended at the end of a proof environment. To substitute a different end-of-proof symbol, use \renewcommand to redefine the command \qedsymbol.

Thus, one might proceed as follows:

\renewcommand{\qedsymbol}{$\blacksquare$}

A mwe to play with:

\documentclass[a4paper,11pt]{article}
\usepackage{amsmath,amssymb,amsthm}

\renewcommand{\qedsymbol}{$\blacksquare$}

\begin{document}
\begin{proof}[Proof of the Main Theorem]
  \begin{equation*}
    G(t)=L\gamma!\,t^{-\gamma}+t^{-\delta}\eta(t) \qedhere
  \end{equation*}
\end{proof}
\end{document}

If you're looking for beamer, it is quite the same: you have to re-define the template qed symbol (almost similar to my previous answer in How to customise (e.g. make thicker) the end-proof symbol in Beamer?).

A mwe:

\documentclass{beamer}

\begin{document}

\begin{frame}
\setbeamertemplate{qed symbol}{$\blacksquare$}
\begin{proof}
\begin{itemize}
\item First item.
\item Second item.
\item Third item.
\end{itemize}
\end{proof}
\end{frame}

\end{document}

Notice that in this case the symbol will assume the colors of the Beamer color theme currently in use.

Thank you very much for \qedhere! – bkarpuz Sep 30 '14 at 08:55 — bkarpuz, Sep 30 '14 at 08:55
@bkarpuz: Glad it helped :) – Claudio Fiandrino Sep 30 '14 at 12:37 — Claudio Fiandrino, Sep 30 '14 at 12:37

score 21 · Answer 2 · answered Feb 15 '13 at 17:41

21

If you are using the amsthm package (or one of the ams documentclasses), then the symbol used is given by the command \qedsymbol. It can be redefined as follows:

Sample output

\documentclass{article}

\usepackage{amsthm,amssymb}

\renewcommand{\qedsymbol}{\rule{0.7em}{0.7em}}

\begin{document}
\begin{proof}
  Clear.
\end{proof}
\end{document}

answered Feb 15 '13 at 17:41

Andrew Swann

95,762

9

Immediately followed, of course, by \begin{self-doubting student}! – OJFord Dec 05 '16 at 23:07

Solid black box in the proof environment

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