# line break in math mode within longtable environment

I have a long mathematical expression within parenthesis which is larger than the column width that I have specified for my table. How do I force it to break the expression onto a new line?

       \begin{center}
\footnotesize
\begin{longtable}[l]{>{\raggedright}p{2.25cm}>{\raggedright}p{9cm}>{\raggedright\arraybackslash}p{3cm}}
\hline
\textbf{Text}  &     \textbf{Maths} &     \textbf{Text} \\ \hline
\multicolumn{3}{c}{{\bfseries \tablename\ \thetable{} -- Continued from previous page}} \\
\hline
\textbf{Text}  &     \textbf{Maths} &     \textbf{Text} \\ \hline
\multicolumn{3}{r}{{-- Continued on next page}} \\
\endfoot
\endlastfoot
TEXT 1 &  $\dfrac{\kappa_{nf}}{\kappa_{f}}= 1+3\left(\dfrac{\dfrac{\kappa_{p}}{\kappa_{f}}-1}{\dfrac{\kappa_{p}}{\kappa_{f}}+2}\right)\phi+ \left(3\left(\dfrac{\dfrac{\kappa_{p}}{\kappa_{f}}-1}{\dfrac{\kappa_{p}}{\kappa_{f}}+2}\right)^{2}+\dfrac{3}{4}\left(\dfrac{\dfrac{\kappa_{p}}{\kappa_{f}}-1}{\dfrac{\kappa_{p}}{\kappa_{f}}+2}\right)^{2}+ \newline \dfrac{9}{16}\left(\dfrac{\dfrac{\kappa_{p}}{\kappa_{f}}-1}{\dfrac{\kappa_{p}}{\kappa_{f}}+2}\right)^{3}\left(\dfrac{\dfrac{\kappa_{p}}{\kappa_{f}}+2}{\dfrac{\kappa_{p}}{2\kappa_{f}}+3}\right)....\right)\phi^{2}$ & Text 2\\

\hline
\end{longtable}
\end{center}
\normalsize


Ideally I would like the break to occur at the just before the \dfrac{9}{16}

I have tried putting a \begin{split} and \end{split} but I get a latex error (Package amsmath Error: \begin{split} won't work here

Has anyone got an idea?

Cheers

• center has no effect on a longtable, other than introduce vertical space. – David Carlisle Oct 1 '14 at 11:24

You can't break a line inside \left...\right, so write \right.\newline\left., where the dot means "invisible delimiter".

By the way, breaking at 3/4 gives a better-looking result.
Personal opinion: I prefer operators be tied to the right operand, so instead of having + signs at the end of line, I'd rather like to place them at the beginning, correctly aligned.

\documentclass[a4paper,10pt,draft]{article}
\usepackage[cm]{fullpage}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{longtable,array}
\newcolumntype{P}[1]{>{\raggedright\arraybackslash}p{#1}}

\begin{document}
\begin{longtable}{P{2.25cm}P{9cm}P{3cm}}
\hline
\textbf{Text}  &     \textbf{Maths} &     \textbf{Text} \\
\hline
\multicolumn{3}{c}{{\bfseries \tablename\ \thetable{} -- Continued from previous page}} \\
\hline
\textbf{Text}  &     \textbf{Maths} &     \textbf{Text} \\ \hline
\multicolumn{3}{r}{{-- Continued on next page}} \\
\endfoot
\endlastfoot
TEXT 1 &  $\dfrac{\kappa_{nf}}{\kappa_{f}} = 1 + 3\left(\dfrac{\dfrac{\kappa_{p}}{\kappa_{f}}-1}{\dfrac{\kappa_{p}}{\kappa_{f}}+2}\right)\phi + \left(3\left(\dfrac{\dfrac{\kappa_{p}}{\kappa_{f}}-1}{\dfrac{\kappa_{p}}{\kappa_{f}}+2}\right)^{2}+\right.\newline \left. \dfrac{3}{4}\left(\dfrac{\dfrac{\kappa_{p}}{\kappa_{f}}-1}{\dfrac{\kappa_{p}}{\kappa_{f}}+2}\right)^{2} + \dfrac{9}{16}\left(\dfrac{\dfrac{\kappa_{p}}{\kappa_{f}}-1}{\dfrac{\kappa_{p}}{\kappa_{f}}+2}\right)^{3} \left(\dfrac{\dfrac{\kappa_{p}}{\kappa_{f}}+2}{\dfrac{\kappa_{p}}{2\kappa_{f}}+3}\right)....\right)\phi^{2}$ & Text 2\\

\hline
\end{longtable}
\end{document}

• Presto! Cheers dude! Can the same be done with a long fraction? – Magiclamarshmallow Oct 1 '14 at 14:58
• Explain better. Placing \newlines between objects is easy, but I think that break inside a fraction it's a very very bad idea, and gives a very poor result. – Astrinus Oct 1 '14 at 15:01
• Like you say it gives a poor result so I think I will just break the fraction into two parts rather than try to split it over two line. Might need to do some algebra! – Magiclamarshmallow Oct 1 '14 at 16:21

A variant, using the nccmath package (for its mediumsized fractions) and the ltablex package, that allows for page breaking within tabularx environments. I use an aligned environment for the long math formula, and replace the \left … \right pairs with \Biggl … \Biggr. The makecell package allows to give some vertical spacing around the formula:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{amssymb}
\usepackage{nccmath}
\usepackage[nomarginpar, showframe]{geometry}
\usepackage{mathtools}
\usepackage{array,ltablex}
\keepXColumns

\usepackage{makecell}
\setcellgapes{4pt}
\makegapedcells

\begin{document}

\setlength\tabcolsep{4pt}
\begin{tabularx}{\linewidth}{|>{\raggedright}p{2.25cm}| >{\footnotesize}X| >{\raggedright\arraybackslash}p{3cm}|}%
\hline
\textbf{Text} & \textbf{Maths} & \textbf{Text} \\ \hline
\multicolumn{3}{c}{{\bfseries \tablename\ \thetable{} -- Continued from previous page}} \\
\hline
\textbf{Text} & \textbf{Maths} & \textbf{Text} \\ \hline
\begin{aligned}\MoveEqLeft[-1.5] \mfrac{κ_{nf}}{κ_{f}}= 1+3\Biggl(\mfrac{\mfrac{κ_{p}}{κ_{f}}-1}{\mfrac{κ_{p}}{κ_{f}}+2}\Biggr)ϕ + {}\\[-1ex] & + \Biggl[3\Biggl(\mfrac{\mfrac{κ_{p}}{κ_{f}}-1}{\mfrac{κ_{p}}{κ_{f}}+2}\Biggr)^{\!2} + \mfrac{3}{4}\Biggl(\mfrac{\mfrac{κ_{p}}{κ_{f}}-1}{\mfrac{κ_{p}}{κ_{f}}+2}\Biggr)^{\!2} + \mfrac{9}{16}\Biggl(\mfrac{\mfrac{κ_{p}}{κ_{f}}-1}{\mfrac{κ_{p}}{κ_{f}}+2}\Biggr)^{\!3} \Biggl(\mfrac{\mfrac{κ_{p}}{κ_{f}}+2}{\mfrac{κ_{p}}{2κ_{f}}+3}\Biggr)....\Biggr]ϕ^{2}\end{aligned}