2

How to achieve nice (non-automatic) long equations breaking, like dmath environment from breqn package does automatically, but using a more common environment, e.g., multline, multlined (from mathtools), or split?

Compare dmath results with the rest. (Note that page size is dictated by the journal requirements.)

\documentclass[10pt,twocolumn]{article}
\usepackage[letterpaper,textwidth=18.5cm,textheight=22.9cm]{geometry}
\usepackage{mathtools}
\usepackage{breqn}

\DeclareMathOperator{\Real}{Re}
\let\oldhat\hat
\renewcommand{\vec}[1]{\mathbf{#1}}
\renewcommand{\hat}[1]{\oldhat{\mathbf{#1}}}
\newcommand{\del}{\boldsymbol{\nabla}}
\newcommand{\taub}{\boldsymbol{\tau}}

\begin{document}

\textbf{dmath:}
\begin{dmath}
\vec{U_{0}} = \left[ H^{-1} \hat{k} \times \del \left( fH^{-1} \right) \right]
\Real \left\{ \, \ointop_{fH^{-1}} \left( \rho^{-1} H^{-1} \taub \right) \cdot d \vec{l} 
\div \ointop_{fH^{-1}} H^{-1} \left( H^{-1} R+ i \omega \right) 
\left( \del \left( fH^{-1} \right) \cdot \vec{n} \right) \, d \vec{l} \right\}.
\end{dmath}

\textbf{multline:}
\begin{multline}
\vec{U_{0}} = \left[ H^{-1} \hat{k} \times \del \left( fH^{-1} \right) \right] 
\Real \left\{ \, \ointop_{fH^{-1}} \left( \rho^{-1} H^{-1} \taub \right) \cdot d \vec{l} \right. \\
\div \left. \ointop_{fH^{-1}} H^{-1} \left( H^{-1} R+ i \omega \right) 
\left( \del \left( fH^{-1} \right) \cdot \vec{n} \right) \, d \vec{l} \right\}.
\end{multline}

\textbf{multlined:}
\begin{equation}
\begin{multlined}
\vec{U_{0}} = \left[ H^{-1} \hat{k} \times \del \left( fH^{-1} \right) \right] 
\Real \left\{ \, \ointop_{fH^{-1}} \left( \rho^{-1} H^{-1} \taub \right) \cdot d \vec{l} \right. \\
\div \left. \ointop_{fH^{-1}} H^{-1} \left( H^{-1} R+ i \omega \right) 
\left( \del \left( fH^{-1} \right) \cdot \vec{n} \right) \, d \vec{l} \right\}.
\end{multlined}
\end{equation}

\textbf{split:}
\begin{equation}
\begin{split}
\vec{U_{0}} &= \left[ H^{-1} \hat{k} \times \del \left( fH^{-1} \right) \right] 
\Real \left\{ \, \ointop_{fH^{-1}} \left( \rho^{-1} H^{-1} \taub \right) \cdot d \vec{l} \right. \\
&\phantom{=} \div \left. \ointop_{fH^{-1}} H^{-1} \left( H^{-1} R+ i \omega \right) 
\left( \del \left( fH^{-1} \right) \cdot \vec{n} \right) \, d \vec{l} \right\}.
\end{split}
\end{equation}

\end{document}
2

I believe that the result can be improved:

\documentclass[10pt,twocolumn]{article}
\usepackage[letterpaper,textwidth=18.5cm,textheight=22.9cm]{geometry}
\usepackage{mathtools,bm}

\DeclareMathOperator{\Real}{Re}
\renewcommand{\vec}[1]{\mathbf{#1}}
\newcommand{\bhat}[1]{\hat{\mathbf{#1}}}
\newcommand{\del}{\bm{\nabla}}
\newcommand{\taub}{\bm{\tau}}

\begin{document}

\begin{equation}
\begin{multlined}
\vec{U_{0}} = \bigl[H^{-1} \bhat{k} \times \del ( fH^{-1})\bigr]
\Real \Biggl\{\ointop_{\,fH^{-1}}\!\! (\rho^{-1} H^{-1} \taub ) \cdot d \vec{l} \\
{}\div\ointop_{\,fH^{-1}}\!\! H^{-1} (H^{-1} R+ i \omega )
( \del ( fH^{-1} ) \cdot \vec{n} ) \, d \vec{l} \Biggr\}.
\end{multlined}
\end{equation}

\end{document}

Notice that I defined \bhat, rather than redefining \hat (which I would never do); redefining \vec is fine. Notice also that I used no \left and \right commands. The braces results in a much nicer size and the spacing around parentheses is correct.

Final touches: \, in the subscript to the integral and \!\! to move the integrand a bit to the left.

The \boldsymbol command is obsolete and should be changed into \bm loading the bm package.

enter image description here

  • To reproduce the dmath output more closely, I would still go for a split. Additionally, when going from \left\{ to \Biggl\{ there is too little space after the \Real. – mafp Dec 17 '12 at 16:31
  • It's questionable whether dmath gives the best result. I don't think so. There should be no space between an operator and a fence. – egreg Dec 17 '12 at 16:32

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.