Adjust equation numbering indent relative to a \newenvironment

Question

I was working on a new environment for the examples I explain for my lecture notes (fancy environment), but when I create an equation using the equation environment within my newly created example environment, this does not obey the indentation that I have placed on my environment. Is this possible?

\documentclass[letterpaper]{article}
\usepackage{fullpage}
\usepackage{amsmath,amssymb,amsthm}
\usepackage[dvipsnames]{xcolor}
\usepackage{tikz}
\usetikzlibrary{shapes.symbols}
\usepackage{lipsum}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Example Environment 
\newcounter{boxnum}
\newenvironment{egenv}[1]{%
\begingroup\addvspace\medskipamount%
  \stepcounter{boxnum}{\sffamily\bfseries\large EXAMPLE
  \tikz [baseline=(char.base)] \node[shape=rectangle,draw=blue!50,inner sep=2.5pt,fill=Cerulean,text=white] (char) {\arabic{boxnum}};%
  \quad{#1}\vskip0.75\baselineskip}
  \setlength{\leftskip}{20pt}%
  \setlength{\rightskip}{20pt}%
  \setlength{\parfillskip}{0pt plus 2fil}
}{%
  \par\hfill{\color{Cerulean}$\blacksquare$}%
  \par\addvspace\medskipamount%
\endgroup
}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\parindent0pt
\begin{document}

\lipsum[2]
\begin{equation}
  (x-h)^2+(y-k)^2=r^2
\end{equation}

\begin{egenv}{Combined (double) Inequalities}
\lipsum[3]
\end{egenv}

\begin{egenv}{Combined (double) Inequalities}
\lipsum[3]
\begin{equation}\label{stdform}
  (x-h)^2+(y-k)^2=r^2
\end{equation}
\begin{equation}\label{stdformnn}
  (x-h)^2+(y-k)^2=r^2
\end{equation}
\lipsum[3]
\end{egenv}
\end{document}

This yields:

Of course I would like the equation numbering to restore its normal right indent outside my environment. I have looked at Changing the apperance of equation numbers with amsmath which seems to do what I want with:

\makeatletter
\let\mytagform@=\tagform@
\def\tagform@#1{\maketag@@@{\bfseries(\ignorespaces#1\unskip\@@italiccorr)}\hspace{20pt}}
\renewcommand{\eqref}[1]{\textup{\mytagform@{\ref{#1}}}}
\makeatother

But the above effect is global. Any help into the matter will greatly appreciated.

Answer 1

There are a couple of ways to fix this- if you don't mind loading a package, then you can use the adjustwidth environment from the changepage package and use

\begin{adjustwidth}{20pt}{20pt}

You could also use a list environment (which is what the changepage package does), which might also help with your 'endmark' (see note below).

Some other notes:

• you'll probably want to use \refstepcounter assuming that you might want to \label and \ref your environment later on
• the 'end mark' is not guaranteed to stay with the environment. you could try and fix this by making a 'no-break-item' as detailed in https://tex.stackexchange.com/a/47586/6621

I've left the list solution commented in the MWE below so that you can play with it if you like.

MWE

\documentclass[letterpaper]{article}
\usepackage{fullpage}
\usepackage{changepage}
\usepackage{amsmath,amssymb,amsthm}
\usepackage[dvipsnames]{xcolor}
\usepackage{tikz}
\usetikzlibrary{shapes.symbols}
\usepackage{lipsum}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Example Environment 
\newcounter{boxnum}
\newenvironment{egenv}[1]{%
\begingroup\addvspace\medskipamount%
  \refstepcounter{boxnum}{\sffamily\bfseries\large EXAMPLE
  \tikz [baseline=(char.base)] \node[shape=rectangle,draw=blue!50,inner sep=2.5pt,fill=Cerulean,text=white] (char) {\arabic{boxnum}};%
  \quad{#1}\vskip0.75\baselineskip}
 % You can experiment with the `list` environment if you like
 % \begin{list}{}{%
 % \setlength{\leftmargin}{20pt}%
 % \setlength{\rightmargin}{20pt}%
 % \setlength{\parfillskip}{0pt plus 2fil}
 % }%
 %\item%
 \begin{adjustwidth}{20pt}{20pt}
}{%
  \par\hfill{\color{Cerulean}$\blacksquare$}%
  %\item\hfill{\color{Cerulean}$\blacksquare$}%
  %\end{list}
  \end{adjustwidth}
  \par\addvspace\medskipamount%
\endgroup
}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\parindent0pt
\begin{document}

\lipsum[2]
\begin{equation}
  (x-h)^2+(y-k)^2=r^2
\end{equation}

\begin{egenv}{Combined (double) Inequalities}
\lipsum[3]
\end{egenv}

\begin{egenv}{Combined (double) Inequalities}
\lipsum[3]
\begin{equation}\label{stdform}
  (x-h)^2+(y-k)^2=r^2
\end{equation}
\begin{equation}\label{stdformnn}
  (x-h)^2+(y-k)^2=r^2
\end{equation}
\lipsum[3]
\end{egenv}
\end{document}