Defining my own proof environment?

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.

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

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.

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} 

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