\documentclass{article} \usepackage{amsmath} \usepackage{mhequ} \def\eref#1{(\ref{#1})} \textwidth 13cm \textheight 22cm \oddsidemargin 0.2cm \topmargin 0.3cm \pagestyle{empty} \begin{document} \title{Using the \texttt{mhequ} package} \author{Martin Hairer} \date{Version 1.72, 9 November 2022} \maketitle \thispagestyle{empty} This package provides two environments: \texttt{equ} for single-line equations and \texttt{equs} for multi-line equations. They behave similarly to the built-in \texttt{equation} and \texttt{amsmath}'s \texttt{align} environments and can essentially be used as drop-in replacements. The main difference is that equation numbers are handled differently: equations are numbered if and only if they have a \verb|\label|, so there is no need for starred versions. This also applies to individual lines in a multiline equation. Also, the \texttt{equs} environment supports blocks of equation with more Since \texttt{mhequ} redefines the \verb|\tag| and \verb|\intertext| commands, it should always be loaded \textit{after} the \texttt{amsmath} package. However, these two commands should still behave correctly inside the \texttt{amsmath} environments. The rest of this document demonstrates the usage of the \texttt{mhequ} package, it is easiest to just read the source code of this document to see how it works. See also the description given at the start of the file \texttt{mhequ.sty}. Here is a simple labelled equation: \begin{equ}[onelab] e^{i\pi} + 1 = 0 \;. \end{equ} Removing or adding the label does not require a change of environment: \begin{equ} e^{i\pi} + 1 = 0 \;. \end{equ} However, if the option \texttt{numberall} is set, then every single equation is numbered. A simple list of equations can be displayed either with one number per equation \begin{align} f(x) &= \sin(x) + 1\;, \label{e:equ1}\\ h(x) &= f(x) + g(x) -3\;, \label{e:equ3} \end{align} \begin{equs} f(x) &= \sin(x) + 1\;, \label{e:equ1}\\ h(x) &= f(x) + g(x) -3\;, \label{e:equ3} \end{equs} or with one number for the whole list \begin{equs}[e:block] f(x) &= \sin(x) + 1\;, \\ h(x) &= f(x) + g(x) -3\;. \end{equs} Of course, it can also have no number at all: \begin{equs} f(x) &= \sin(x) + 1\;, \\ h(x) &= f(x) + g(x) -3\;. \end{equs} The command \verb|\minilab{label_name}| allows us to create a counter for the lines in a block of equations. \minilab{otherlabel} \begin{equs} f(x) &= \sin(x) + 1\;, \label{e:f}\\ g(x) &= \cos(x) - x^2 + 4\;,\label{e:g}\\[3mm] h(x) &= f(x) + g(x) -3\;. \label{e:h} \end{equs} One can refer to the whole block \eref{otherlabel} or to one line, like \eref{e:f} for example. It is possible to use any tag one likes with the \verb|\tag{displayed_tag}| command \begin{equ}[mylabel] x = y\;, \tag{$\star$} \end{equ} which in this case was used as \verb|\tag{$\star$}|. Such an equation can be referred to as usual: \eref{mylabel}. Of course, \texttt{mhequ} can be used in conjunction with the usual \texttt{equation} environment, but \texttt{mhequ} is great, so why would you want to do this? \begin{equation} x=y+z \end{equation} Typesetting several columns of equations is quite easy and doesn't require 10 different environments with awkward names: \begin{equs} x&=y+z &\qquad a&= b+c &\qquad x&= v \label{laba}\\ x&=y+z &\qquad a&= b+c &\qquad x&= u+1\tag{\ref{laba}'}\label{labtag}\\ \multicol{4}{\text{(multicol)}} &\qquad x&=y \\ a&= b &\multicol{4}{\qquad\text{(multicol)}} \\ x&=y+z &\qquad a^2&= (b-c)^3 +y \\ \intertext{and also (this is some \texttt{\string\intertext})} x&=y+z &\qquad a&= (b+c)^2 - 5 &\qquad \ell&= m\label{labb} \end{equs} We can even extend the block \eref{otherlabel} much later using the \verb|\minilab{label_name}| command: \minilab{otherlabel} \begin{equs} x&=y+z &\quad x&=y+z &\quad f(x)&= b\label{e:x1}\\ x&=y+z & x&=y+z &\quad g(x)&= b\label{e:x2} \\ \multicol{6}{\sin^2 x + \cos^2 x = 1} \label{e:x3} \end{equs} It is possible to change the type of subnumbering and to use the \texttt{\string\text} command without having to load \texttt{amstext}: \setlabtype{Alph} \minilab{alab} \begin{equs} I_1 &= \int_a^b g(x)\,dx\;,&\quad&\text{(First equation)} \label{e:1}\\ I_2 &= \int_a^b g(x^2-1)\,dx\;.&\quad&\text{(Second equation)} \label{e:2} \end{equs} \end{document}