46

Is there an easy way to put a box around a theorem in LaTeX? For example to state an important theorem.

I tried using page 20 of the ntheorem documentation, but I do not know how to use the package.

1
  • ntheorem uses pstricks to shade theorem. So you have to compile via latex-ps-pdf or xelatex. -- Maybe the package framed is helpful. Nov 26, 2011 at 23:43

5 Answers 5

47

You can use \newmdtheoremenv from the mdframed package:

\documentclass{article}
\usepackage{mdframed}
\usepackage{lipsum}

\newmdtheoremenv{theo}{Theorem}

\begin{document}

\begin{theo}
\lipsum*[1]
\end{theo}

\end{document}

enter image description here

If you only want to frame some theorems, then you can define a new environment using the mdframed environment and some previously defined theorem-like environment:

\documentclass{article}
\usepackage{mdframed}
\usepackage{lipsum}

\newtheorem{theo}{Theorem}
\newenvironment{ftheo}
  {\begin{mdframed}\begin{theo}}
  {\end{theo}\end{mdframed}}

\begin{document}

\begin{ftheo}
\lipsum*[1]
\end{ftheo}

\begin{theo}
\lipsum*[1]
\end{theo}

\end{document}
9
  • 1
    Thank you for the effort.For some reason I don't get the whole box: I miss the bottom and left line.
    – Nadori
    Nov 27, 2011 at 0:05
  • @Nadori are you sure it's not only a viewer issue? Nov 27, 2011 at 0:11
  • 1
    @Nadori: No there are no problems ;-) Nov 27, 2011 at 0:26
  • 6
    @Nadori: I noticed that you've received some good answers to your other questions, but you haven't accepted any of them. Please consider marking those answers that you consider to be the best as ‘Accepted’ by clicking on the tickmark below their vote count. This shows which answer helped you most, and it assigns reputation points to the author of the answer (and to you!). Nov 27, 2011 at 0:36
  • 1
    how can i get rid of the enumeration? Apr 27, 2020 at 23:53
44
+50

I don't know if the tcolorbox package was available at the time that the question was asked, but here's a small example taken directly from the documentation:

screenshot

% arara: pdflatex
\documentclass{article}

\usepackage{tcolorbox}
\tcbuselibrary{theorems}

\newtcbtheorem[number within=section]{mytheo}{My Theorem}%
{colback=green!5,colframe=green!35!black,fonttitle=\bfseries}{th}

\begin{document}
\begin{mytheo}{This is my title}{theoexample}
  This is the text of the theorem. The counter is automatically assigned and,
  in this example, prefixed with the section number. This theorem is numbered with
  \ref{th:theoexample} and is given on page \pageref{th:theoexample}.
\end{mytheo}

\end{document}
2
  • 4
    Beautiful! How could you get rid of the numbering?
    – Cris
    Aug 26, 2020 at 8:39
  • Normally you add * to get rid of numbering in Latex, here I use \begin{mytheo*}.. \end{mytheo*} to get rid of the numbering.
    – xue
    Nov 19, 2022 at 3:38
10

Here's a minimum working example (MWE) of how one can use the ntheorem and framed packages to draw a rectangular frame around a theorem environment:

\documentclass{article}
\usepackage{framed} % or, "mdframed"
\usepackage[framed]{ntheorem}
\newframedtheorem{frm-thm}{Theorem}
\begin{document}
\begin{frm-thm}[Pythagoras]
Let $a$, $b$, and $c$ denote the lengths of the sides of a \emph{right 
triangle}, i.e., of a triangle with one angle equal to $90^\circ$. 
Without loss of generality assume that $a\le b<c$. Then
\[ a^2+b^2=c^2. \]
\end{frm-thm}
\end{document}

enter image description here

Check the user guides of the framed and mdframed packages for available options for setting the style of the frame.

5

Here's an example of how you can put some colour into your Theorems using ntheorem combined with PSTricks.

screenshot

\documentclass{article}

\usepackage{pstricks}
\usepackage{pst-grad}
\usepackage{framed}
\usepackage[framed]{ntheorem} 
\usepackage{lipsum}

% framed theorem, red background
\theoremstyle{plain}
\theoremsymbol{}
\theoremseparator{}
\def\theoremframecommand{%
      \psshadowbox[fillstyle=solid,fillcolor=red,linecolor=black]}
\newshadedtheorem{mytheorem}{Special Theorem}

% framed theorem, gradient shading
\theoremstyle{plain}
\theoremsymbol{}
\theoremseparator{}
\def\theoremframecommand{%
      \psshadowbox[fillstyle=gradient,gradbegin=red,gradend=yellow,linecolor=black]}
\newshadedtheorem{myfancytheorem}{Sunset special theorem}

\begin{document}

\begin{mytheorem}
\lipsum[1] 
\end{mytheorem}

\begin{myfancytheorem}
 \lipsum[1]
\end{myfancytheorem}

\end{document}

Either run the above code with

latex myfile.tex
dvips myfile.dvi
ps2pdf myfile.ps

or

xelatex myfile.tex

If you want to run it with pdflatex then add the option pdf to the pstricks load

\usepackage[pdf]{pstricks}

and compile with

pdflatex -shell-escape myfile.tex
2

If you are using thmtools, it should be noted that it can render boxed theorems per se. Example:

\documentclass{report}
\usepackage{thmtools}
\usepackage{lipsum}

\declaretheorem[
  shaded={rulecolor=black, rulewidth=1pt, bgcolor=magenta},
  name=Theorem,
]{thmboxed}

\begin{document}

\begin{thmboxed}
\lipsum[1]
\end{thmboxed}

\end{document}

renders as

this

2
  • how do you suppress the theorem 1 in the title?
    – fdzsfhaS
    Mar 16, 2020 at 21:53
  • @DavidWarrenKatz what are you trying to achieve? Just a colored box with floating text inside? While it's possible to misuse thmtools for that by e.g. setting headformat and headpunct to \@empty in the custom theorem style, a better solution would be using boxes, e.g. a \coloredbox around a \minipage.
    – hoefling
    Mar 16, 2020 at 22:25

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .