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I am using Overleaf to type up a paper involving proof of different results and I would like to write the box at the end of a proof that means QED ie end of proof. How can I do that? Thanks.

I am using

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{amssymb}
4
  • 8
    Do \usepackage{amsthm} and use \begin{proof}...\end{proof} for the proofs. The QED symbol will magically appear.
    – egreg
    Sep 29, 2020 at 21:09
  • @egreg thanks for that, it works brilliantly :) Sep 29, 2020 at 21:14
  • 2
    Just make sure to load amsmath before amsthm. Otherwise the QED symbol can appear out of place in some environments. See this question for example.
    – Sandy G
    Sep 29, 2020 at 21:53
  • @SandyG thanka a lot, your answer to that question is extremely helpful! Sep 30, 2020 at 11:03

1 Answer 1

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As @egreg said in the comments, you can use the proof environment from amsthm, which will automatically place a QED symbol at the end of the proof. You can also use the command \qedsymbol, also from amsthm, to place a QED symbol anywhere. Here's an example of both options, with the preamble you provided.

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{amsthm}

\begin{document}

\begin{proof}
A proof written in the \verb|proof| environment. The QED symbol will appear at the end. 
\end{proof}

A \qedsymbol{} outside of a \verb|proof| environment. 

\end{document} 

In fact, amsthm uses the command \qedsymbol to place the symbol at the end of the proof environment, so if you want to use something else as a QED symbol (for example a black square), you can simply redefine \qedsymbol, and the proof environment will use it.

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