Take the 2-minute tour ×
TeX - LaTeX Stack Exchange is a question and answer site for users of TeX, LaTeX, ConTeXt, and related typesetting systems. It's 100% free, no registration required.

I want to create an environment star Exercise, but I can not. Please help me.

\documentclass{book} 
    \usepackage{amsfonts}
    \usepackage{amssymb}
    \usepackage{amsmath}
    \newtheorem{ex}{Exercise}[chapter]
    \begin{document}
    \chapter{First Chapter}
    \section{First section}
    \begin{ex}
    This is an Exercise
    \end{ex}

    \begin{ex}
    This is an Exercise
    \end{ex}

    \end{document}

If next is a difficult Exercise, how to define new environment Exercise star, for example \textbf{Exercise} $1.3^\text{*}$.

share|improve this question
1  
What do you want? Please explain your intention? –  Marco Daniel Oct 20 '12 at 7:04
    
An alternative to the nice (accepted) answer: write the ex environment so that it accepts an optional * argument. That's easy with the xparse package. –  Ethan Bolker Oct 20 '12 at 13:30

3 Answers 3

up vote 12 down vote accepted

Just modify the representation of the counter for difficult exercises:

\documentclass{book}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsmath}
\newtheorem{ex}{Exercise}[chapter]
\newenvironment{ex*}
  {\renewcommand\theex{\thechapter.\arabic{ex}\rlap{$^*$}}\ex}
  {\endex}


\begin{document}
\chapter{First Chapter}
\section{First section}
\begin{ex}
This is an Exercise
\end{ex}

\begin{ex}
This is an Exercise
\end{ex}

\begin{ex*}
This is a difficult Exercise
\end{ex*}

\end{document}

enter image description here


If the asterisk is not desired in the references to this exercise, then the definition of ex* can be changed into

\makeatletter
\newenvironment{ex*}
  {\renewcommand\theex{\thechapter.\arabic{ex}\rlap{$^*$}}%
   \ex\edef\@currentlabel{\thechapter.\arabic{ex}}}
  {\endex}
\makeatother

so that the reference will be created without *.

share|improve this answer
    
I had a problem like this once. I can use it again. Thanks @egreg. –  hpesoj626 Oct 20 '12 at 7:29
    
@hpesoj626 There may be a problem if you want to \label the exercise and then refer to it: with this solution the * will be printed also by \ref. It can be changed, if needed: please, let me know –  egreg Oct 20 '12 at 7:31
    
Yes I see the *. Can you update the answer to so that the asterisk is not included by \ref? I was supposed to ask in chat but connection is slow at the moment. –  hpesoj626 Oct 20 '12 at 7:50
    
@hpesoj626 I've put the addition you requested. –  egreg Oct 20 '12 at 19:44
    
Thanks. What does the new line \ex\edef\@currentlabel{\thechapter.\arabic{ex}} actually do? I don't know what \edef does to \@currentlabel. Is there already a question here or material that explains these? Let me know if I have to ask this in a separate post or in chat. Thanks. –  hpesoj626 Oct 20 '12 at 23:20

The package Exercise can help here:

\documentclass{article}

\usepackage{exercise}

\begin{document}
\begin{Exercise}
    This is an exercise.
\end{Exercise}

\begin{Exercise}[difficulty=1]
    This is a difficult exercise.
\end{Exercise}
\end{document}

The result:

Example of exercise package

share|improve this answer

I have just found an answer

 \documentclass[12pt,openany,twoside]{book} 
\usepackage{fouriernc}
\usepackage[thmmarks,standard,thref]{ntheorem}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsmath}

\theoremseparator{.}
\theorembodyfont{\upshape}
\newtheorem{ex}{Exercise}[chapter]
\theoremseparator{$^\text{*}$.}
\newtheorem{dex}[ex]{Exercise}

\usepackage{answers}
\Newassociation{sol}{Answer}{loigiaichung}
\Newassociation{sols}{ansF}{loigiaichung}         
\newcommand{\preansF}{}                               
\renewcommand{\ansFlabel}[1]{{\bfseries #1*.}}         
\renewcommand{\Answerlabel}[1]{\bfseries #1.}
\begin{document}
\chapter{First Chapter}
\Opensolutionfile{loigiaichung}[ex]
\section{First section}
\begin{ex}
This is an exercise
\begin{sol}
This is a solution
\end{sol}
\end{ex}

\begin{dex}
This is an exercise
\begin{sols}
This is a solution
\end{sols}
\end{dex}


\chapter{Second Chapter}
\Opensolutionfile{loigiaichung}[ex]
\section{Second  section}
\begin{ex}
This is an exercise
\begin{sol}
This is a solution
\end{sol}
\end{ex}

\begin{dex}
This is an exercise
\begin{sols}
This is a solution
\end{sols}
\end{dex}

\Closesolutionfile{loigiaichung}
\section{Hint, anserw}
\input{ex}

\end{document}
share|improve this answer
    
You shouldn't be using $^\text{*}$, which produces too high an asterisk: either $^{*}$ or simply *. However, the position of the asterisk will be wrong if you use the optional argument to dex: \begin{dex}[From \cite{xyz}] will have the asterisk after the attribution. –  egreg Oct 20 '12 at 22:12

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.