Example environment

Question

I want an example environement that put Example 1.2 in the margin (bold) Text of example in the textwidth, Solution in the margin (italics) and the text of solution in the text width.

Answer 1

Solution 1

Here's something to get you going using the ntheorem package.

% arara: pdflatex
\documentclass{article}
\usepackage{ntheorem}   % needed for theorems, examples- MUST load AFTER amsmath
\usepackage{lipsum}

\makeatletter
\newtheoremstyle{margincmh}%
{\item[\theorem@headerfont \llap{##1 ##2}]}%
{\item[\theorem@headerfont \llap{##1 ##2} -- ##3\theorem@separator\hskip\labelsep]}%

\newtheoremstyle{margincmhsoln}%
{\item[\theorem@headerfont \llap{##1}]}%
{\item[\theorem@headerfont \llap{##1} (##3): ]}%
\makeatother

% example
\theoremstyle{margincmh}
%\theorembodyfont{\itshape}}
\theorembodyfont{}
\theoremsymbol{}
\theoremprework{\medskip}
\theorempostwork{}
\theoremseparator{:}
\newtheorem{myexample}{example}

% solution
\theoremstyle{margincmhsoln}
\theorembodyfont{}
\theoremheaderfont{\itshape}
\theoremprework{\medskip}
\theoremseparator{}
\newtheorem{mysolution}{Solution}

\begin{document}

\begin{myexample}
\lipsum[1]  
\end{myexample}
\begin{mysolution}
 \lipsum[2] 
\end{mysolution}
\end{document}

Solution 2

Alternatively, if you'd prefer to make the environment yourself without a theorem package, you can create it as a simple list- I have used the enumitem package to help with the margins

% arara: pdflatex
\documentclass{article}
\usepackage{lipsum}
\usepackage{enumitem}

\newcounter{myexample}
\newenvironment{myexample}{\refstepcounter{myexample}\itemize[leftmargin=0mm]\item[\bfseries example \themyexample]}{\enditemize}

\newenvironment{mysolution}{\itemize[leftmargin=0mm]\item[\itshape Solution]}{\enditemize}

\begin{document}

\begin{myexample}
\lipsum[1]  
\end{myexample}
\begin{mysolution}
  \lipsum[1]
\end{mysolution}
\end{document}

Answer 2

Here is a possibility with exsheets:

\documentclass{article}

\usepackage[load-headings]{exsheets}
\SetupExSheets{
  counter-within = section ,
  headings = margin ,
  counter-format = se.qu
}

\RenewQuSolPair
  {question}
  {solution}[print][headings-format=\itshape]

\usepackage{lipsum}% dummy text

\begin{document}

\section{Foo}

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

\begin{solution}
  \lipsum[2] 
\end{solution}

\end{document}

Hiding the number of the solution is possible but requires a little bit more work:

\documentclass{article}

\usepackage[load-headings]{exsheets}

\DeclareInstance{exsheets-heading}{margin-no-nr}{default}{
  runin = true ,
  title-post-code = \space ,
  attach = { main[l,vc]title[r,vc](0pt,0pt) }
}

\SetupExSheets{
  counter-within = section ,
  counter-format = se.qu
}

\RenewQuSolPair
  {question}[name=Example][headings=margin]
  {solution}[print][headings=margin-no-nr,headings-format=\itshape]

\usepackage{lipsum}% dummy text

\begin{document}

\section{Foo}

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

\begin{solution}
  \lipsum[2] 
\end{solution}

\end{document}