# Defining my own proof environment?

How would I define a proof environment that is basically used with

\begin{proof}
some proof here
\end{proof}


and it would be equivalent to:

\paragraph{Proof:} some proof here
\hfill \box


?

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You probably want to add a “qed” box at the end of a proof. For this, it is enough to load a package such as amsmath. –  Juan A. Navarro Feb 3 '11 at 7:25
Environments for proofs, theorems etc. are provided by either the amsthm or the ntheorem package. –  Carsten Thiel Feb 3 '11 at 8:34

With LaTeX syntax:

\newenvironment{proof}{\paragraph{Proof:}}{\hfill$\square$}


I assume here that you mean \hbox{} not \box in your code. The \null macro is short for \hbox{}. The \box is a TeX primitive and is more like \usebox.

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this "box" at the end is quite invisible. and if the proof ends with a display or a list, there's an extra blank line. –  barbara beeton May 21 '13 at 21:29
@barbarabeeton: It was not my original intension to draw a real box there because I took the \box macro of the OP with it's normal TeX meaning ;-) I modified the answer now to draw a real box. I don't have a quick fix for blank line issue. IMHO Someone should post an answer based on amsthm or a similar package. –  Martin Scharrer May 22 '13 at 6:44
This solution gave me an extra blank line at the beginning. Replacing \paragraph{Proof:}} with \textbf{Proof:} solved the problem. –  ntc2 Jan 28 at 4:46
@ntc2, I'm guessing that was an indent from \paragraph{} which can be suppressed with \noindent –  PatrickT Feb 1 at 22:22

You can also use the amsthm package which is a really nice and quick way of creating a proof.

Implementation

\documentclass{article}
\usepackage{amsthm}

\begin{document}
\begin{proof}
\end{proof}

\end{document}


It will add Proof in italics at the beginning of the text given as argument and a white square (Q.E.D. symbol) at the end of it.

I found this easy solution at 1. You can also look up there how you define your own environments using this package.

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Welcome to TeX.SX! –  Papiro Jun 11 '13 at 22:18
\def\QEDmark{\square}
\def\proof{\paragraph{Proof:}}
\def\endproof{\hfill\QEDmark}

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this one seems to be giving an error about \begin{document} missing whenever I try to use \begin{proof} \end{proof} –  kloop Feb 2 '11 at 23:46
@kloop: I think it's the problem Martin pointed out - \box is a Tex primitive that looks ahead for the box number, and I guess then will eat the closing parenthesis. I've changed the code. –  Charles Stewart Feb 2 '11 at 23:58
@kloop: BTW, you can vote up as well as accept Martin's answer. –  Charles Stewart Feb 2 '11 at 23:59
Aaahhh, he meant to draw a box using \box, ok ... I sometimes I think to complicated. –  Martin Scharrer Feb 3 '11 at 0:20
The \square should be enclosed in $ signs: \def\QEDmark{$\square$}. – user31011 May 21 '13 at 3:10 show 1 more comment This is a solution using the ntheorem package. Here some explanations: • amssymb is loaded to use \blacksquare • The package ntheorem is loaded using the option thmmarks to support the placement of endmarks. • \theoremheaderfont{\bfseries} sets the theorem title in bold. • \theorembodyfont{\normalfont} preserves the normal text font for the theorem content. • \theoremseparator{:} set : to be the separator between title and content. • \theoremsymbol{$\blacksquare$} will place a solid black square at the end of every theorem environment. • \newtheorem*{proof}{Proof} sets up a new unnumbered environment named proof with the default title "Proof". Afterwards you can use \begin{proof} ... \end{proof} just like any other environment. Implementation \documentclass{article} \usepackage{amssymb} \usepackage[thmmarks]{ntheorem} \theoremheaderfont{\bfseries} \theorembodyfont{\normalfont} \theoremseparator{:} \theoremsymbol{$\blacksquare\$}
\newtheorem*{proof}{Proof}
\begin{document}
\begin{proof}
We immediately see, that
$1 + 1 = 2.$
Thus the proof is done.
\end{proof}
\end{document}


Output

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the box won't be there if the proof ends with a display or a list. regarding ending with a display, that's not great style; better to finish off with text as in this example. but a list might be harder to avoid. –  barbara beeton May 21 '13 at 21:23
Actually in some case the box will be there when ending with a dislay (although the order of appearance seems very random to me). Nevertheless I agree with you on the style issue. –  Henri Menke May 21 '13 at 21:37