[OS X TeX] environment question

[Art Werschulz]

Hi.

I have created an environment called "offset", which I use for  
material that needs to be offset from the main text flow.  Here is a  
small LaTeX file that illustrates its definition and use.

<snip>
\documentclass{article}

\newenvironment{offset}[1]%
   {\bigskip\hrule\nopagebreak[4]\bigskip\nopagebreak[4]\noindent%
       \textbf{#1}\nopagebreak\par\medskip\nopagebreak\noindent}%
   {\nopagebreak[4]\bigskip\hrule\bigskip}

\begin{document}
My first example is
\begin{offset}{Addition rule (elementary version)}%
   Given two disjoint events, $E_1$ and $E_2$, with associated
   probabilities P($E_1$) and P($E_2$), the probability of $E_1$
   \emph{or} $E_2$ occurring is equal to
   to $P(E_1) + P(E_2)$.  That is,
   \[P(E_1 \cup E_2) = P(E_1) + P(E_2)\]
   if $E_1$ and $E_2$ are disjoint.
\end{offset}
As you can see, this looks pretty good.

My second example is:
\begin{offset}{Addition rule (general version)}%
    Given events $E_1$ and $E_2$, with associated
    probabilities $P(E_1)$ and $P(E_2)$, the probability of $E_1$
    \emph{or} $E_2$ occurring is
    \[P(E_1\cup E_2) = P(E_1) + P(E_2) - P(E_1 \cap E_2)\]
\end{offset}
That extra space between the math display and the horizontal line is
ugly.

\end{document}
</snip>

Note the following:
(1) The comment about the extra (vertical) space.
(2) I need to put a % after the argument, to avoid an extra horizontal  
space.
Any ideas how to fix this?  Is there something pre-existing that I can  
use instead?

Thanks.

Art Werschulz
207 Stoughton Avenue, Cranford  NJ 07016-2838
(908) 272-1146