Text Formatting ⇒ Numbering theorem within chapter

[localghost]

Not sure if this is what you mean by an MWE, but however; [...]

What do you think was the link for?

According to the style declaration the counter of the »opgave« theorem like environment contains the section counter. So you have to use the \section command first to have a full enumeration for this environment.

Code: Select all

\documentclass[12pt,a4paper,dutch]{article} 
\usepackage[T1]{fontenc}
\usepackage[latin1]{inputenc}
\usepackage{babel}
\usepackage[includeheadfoot,margin=2cm]{geometry}
\usepackage{amsmath}
\usepackage{amsfonts,amssymb,amsthm}

\theoremstyle{plain}                            
\newtheorem{opgave}{Opgave}[section]

\begin{document}
  \section{Secton One}
  \setcounter{opgave}{3}
  \begin{opgave}
    Show that  $|b| \leq a$ if and only if $ -a \leq b \leq a$. 
  \end{opgave}
\end{document}

The environment is numbered within a section thus the counter opgave is reset with every new \section command.

[Hanneke]

Ah, I didn't know I had to change the section as well, but actually it's quite logic. Thanks!

I've changed the enumerate, but the a4wide is a bit different from a4paper, sometimes I prefer a4wide, so why wouldn't I keep it? Most of my documents are for private use only.

[Hanneke]

Not sure if this is what you mean by an MWE, but however; [...]

What do you think was the link for?

I read it, at least a bit. But I was expecting that an MWE would be made with a program or whatever. Since I couldn't find that on the page you directed my too, I thought that wouldn't be it, but I still was not sure wheter it was just my code.

[magicmoose]

An MWE is a fully compilable document with only what is required to generate your error. Start with the full document you are working on and remove everything until the error goes away, then add the last bit you removed. Remove all packages that aren't used, all preamble (new commands etc. that aren't used) and everything between \begin{document} and \end{document} that you can without losing the error. This is a good example from gmedina

Code: Select all

\documentclass[a4paper,12pt]{article} 
\usepackage{amsmath, amsfonts, amssymb, amsthm, amsrefs}
\usepackage[dutch]{babel}

\theoremstyle{plain}                            
\newtheorem{opgave}{Opgave}[section]

\begin{document}

\setcounter{section}{3}
\setcounter{opgave}{3}
\begin{opgave}
Show that  $|b| \leq a$ if and only if $ -a \leq b \leq a$. 
\end{opgave}

\end{document}

[Hanneke]

Thanks, next time, I will post that directly.

[localghost]

[...] the a4wide is a bit different from a4paper, sometimes I prefer a4wide, so why wouldn't I keep it? Most of my documents are for private use only.

Obsolete packages and classes can cause trouble when used together with modern ones in one document. Searching the error may cost a lot of time then.