# [OS X TeX] Exercises

George Gratzer gratzer at me.com
Fri Apr 10 18:56:33 CEST 2009

In my new book, I have exercises at the end of each section. I use the
xcb environment from amsbook.cls:

\newenvironment{xcb}{%
\setcounter{enumi}{0}%
\settowidth{\leftmargini}{\labelenumi\hskip\labelsep}%
\setcounter{enumii}{4}% letter d
\settowidth{\leftmarginii}{\labelenumii\hskip\labelsep}%
\@startsection{section}% counter name; ignored because of the
% * below
{1}% sectioning level
{\z@}% indent to the left of the section title
{18\p@\@plus2\p@}% vertical space above
{1sp}% Space below of 13pt base-to-base, so none needs to be added
% here; but \z@ would cause the following text to be run-in, so
we
% use 1sp instead.
{\bfseries}% The font of the subsection title
*% always unnumbered
}{%
\par
}

modified as follows:

\newenvironment{exercises}
{
\begin{xcb}{}\noindent\textbf{Exercises}
\begin{enumerate}
\renewcommand{\labelenumi}{\theenumi.}
\settowidth{\leftmargini}{NN.\hskip\labelsep}
}
{\end{enumerate}\end{xcb}}

and then

\begin{exercises}

\item

\begin{exercises}

works well.

Problem: I want the difficult exercises marked with a *:

25*.

How could I do that? How do I modify one number, without effecting the
rest?

GG