Fancy box around equation

Question

I am trying to get my equations to show up like:

This is my attempt thus far:

\documentclass[11pt,fleqn]{book} 
\usepackage[top=3cm,bottom=3cm,left=3.2cm,right=3.2cm,headsep=10pt,a4paper]{geometry} 

\usepackage{xcolor}
\definecolor{ocre}{RGB}{243,102,25}
\usepackage{avant} 
\usepackage{empheq}
\usepackage{mathptmx}

\usepackage{microtype} 
\usepackage[utf8]{inputenc} 
\usepackage[T1]{fontenc} 
\usepackage{calc} 
\begin{document}

\newcommand*\Ocrebox[2][Example]{%
\sbox{\mysaveboxM}{#2}%
\sbox{\mysaveboxT}{\fcolorbox{ocre}{ocre!10}{#1}}%
sbox{\mysaveboxM}{%
\parbox[b][\ht\mysaveboxM+.5\ht\mysaveboxT+.5\dp\mysaveboxT][b]{%
\wd\mysaveboxM}{#2}%
}%
\sbox{\mysaveboxM}{%
\fcolorbox{black}{shadecolor}{%
\makebox[\linewidth-10em]{\usebox{\mysaveboxM}}%
}%
}%
\usebox{\mysaveboxM}%
\makebox[0pt][r]{%
\makebox[\wd\mysaveboxM][c]{%
\raisebox{\ht\mysaveboxM-0.5\ht\mysaveboxT
+0.5\dp\mysaveboxT-0.5\fboxrule}{\usebox{\mysaveboxT}}%
}%
}%
}

\begin{empheq}[box=\Ocrebox]
\frac{C(s)}{R(s)}= \frac{G(s)}{1+G(s)H(s)}
\label{e5}
\end{empheq}

\end{document}

I am not getting this to compile though. Any help will be greatly appreciated!

Answer 1

For the frame around theorem-like structures, one possibility is to use mdframed and amsthm; for a simple frame around equations, empheq-style, it's enough to say something like:

\newcommand*\mymathbox[1]{%
  \fcolorbox{ocre}{mygray}{\hspace{1em}#1\hspace{1em}}}

and then use box=\mymathbox in the optional argument of empheq. A complete example:

\documentclass{book}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{amsthm}
\usepackage{empheq}
\usepackage{bookman}
\usepackage[framemethod=tikz]{mdframed}

\definecolor{ocre}{RGB}{243,102,25}
\definecolor{mygray}{RGB}{243,243,244}

\newcommand*\mymathbox[1]{%
  \fcolorbox{ocre}{mygray}{\hspace{1em}#1\hspace{1em}}}

\newtheoremstyle{mystyle}
  {\topsep}
  {\topsep}
  {\normalfont}
  {}
  {\sffamily\bfseries}
  {.}
  {.5em}
  {{\color{ocre}\thmname{#1}~\thmnumber{#2}}\thmnote{\,--\,#3}}%
\theoremstyle{mystyle}
\newmdtheoremenv[
  backgroundcolor=mygray,
  linecolor=ocre,
  leftmargin=20pt,
  innerleftmargin=0pt,
  innerrightmargin=0pt,
  ]{theo}{Theorem}[section]

\begin{document}

\chapter{Test chapter}
\section{Test section}

\begin{theo}[Name of the theorem]
In $E=\mathbb{R}^n$ all norms are equivalent.
\begin{align}
a &= b\\
E &= mc^2 + \int_a^a x\, \mathrm{d}x
\end{align}
\end{theo}

\begin{empheq}[box=\mymathbox]{align}
a&=b\\
E&=mc^2 + \int_a^a x\, \mathrm{d}x
\end{empheq}

\end{document}

In a comment, it has been requested to have a framed box similar for those for theorems in my previous solution, but for math expressions; one possibility here is to use the tcolorbox package:

\documentclass{book}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{amsthm}
\usepackage{bookman}
\usepackage[most]{tcolorbox}

\definecolor{ocre}{RGB}{243,102,25}
\definecolor{mygray}{RGB}{243,243,244}

\tcbset{myformula/.style={
  arc=0pt,
  outer arc=0pt,
  colback=mygray,
  colframe=ocre,
  boxrule=0.4pt,
  left=2pt,
  right=2pt,
  highlight math style={
    arc=0pt,
    outer arc=0pt,
    colback=mygray,
    colframe=red.
    }
  }
}

\begin{document}

\chapter{Test chapter}
\section{Test section}

\begin{tcolorbox}[ams equation,myformula]
E = mc^2 + \int_a^a x\, \mathrm{d}x
\end{tcolorbox}

\begin{tcolorbox}[ams align,myformula]
a &= b \\
E &= mc^2 + \int_a^a x\, \mathrm{d}x
\end{tcolorbox}

\end{document}

Or, using mdframed again,

\documentclass{book}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{amsthm}
\usepackage{bookman}
\usepackage[framemethod=tikz]{mdframed}

\definecolor{ocre}{RGB}{243,102,25}
\definecolor{mygray}{RGB}{243,243,244}

\newmdenv[
  innertopmargin=0pt,
  backgroundcolor=mygray,
  linecolor=ocre,
  innerleftmargin=0pt,
  innerrightmargin=0pt,
  leftmargin=10pt
  ]{mymath}

\begin{document}

\chapter{Test chapter}
\section{Test section}

\begin{mymath}
\begin{align}
a &= b\\
E &= mc^2 + \int_a^a x\, \mathrm{d}x
\end{align}
\end{mymath}

\end{document}