Defining my own proof environment?

Question

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

?

Answer 1

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.

Answer 2

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}
    Your proof here.
\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.

Answer 3

A small extension due to the case that the proofs are in the section "Proofs:"

\documentclass[11pt]{amsart}
\newtheorem{pro}{Proposition}[section]
\newtheorem{theo}[pro]{Theorem}

\newenvironment{myproof}[2] {\paragraph{Proof of {#1} {#2} :}}{\hfill$\square$}
\begin{document}
\begin{theo} \label{theo}
Hello
\end{theo}

\begin{myproof}{Theorem}{\ref{theo}}
This is the proof
\end{myproof}
\end{document}

Answer 4

\def\QEDmark{\ensuremath{\square}}
\def\proof{\paragraph{Proof:}}
\def\endproof{\hfill\QEDmark}

Answer 5

I use ams package and changed a predefined "proof" environment in the following way and it works for me in LaTeX:

\renewenvironment{proof}{{\bf \emph{Proof.} }}{\hfill $\Box$ \\} 

It changes the "proof" word to an italic bold "Proof.", adds a white QED. mark at the end of the last line of the proof, and creates a line space from whatever comes after the proof.

Answer 6

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