# Problem splitting/fitting equation

I am struggling with an equation that exceeds the page, as it is very long. I have already read that the best solution is splitting the equation, so I have tried using {multline} or {split}, but I keep getting errors. Can anybody help me?

    \begin{aligned} i\to -\frac{-c \left(\beta (-2 \gamma -\delta +\nu )+\sqrt{\beta ^2 (\delta +\mu )^2+c^2 (\nu +\mu )^2+2 \beta c (\nu +\mu ) (2 \gamma +\delta +\mu )}\right)+\beta \left(\beta \delta +\beta \mu +\sqrt{\beta ^2 (\delta +\mu )^2+c^2 (\nu +\mu )^2+2 \beta c (\nu +\mu ) (2 \gamma +\delta +\mu )}\right)+c^2 (\nu +\mu )}{2 \beta ^2 c} \end{aligned}


Thank you :-)

I would reorganize the terms and avoid the big fraction:

\documentclass{article}
\usepackage{amsmath}

\begin{document}

$$\begin{split} i\to \frac{1}{2 \beta^2 c} \Bigl( & c\sqrt{\beta ^2 (\delta +\mu )^2+c^2 (\nu +\mu )^2 +2 \beta c (\nu +\mu ) (2 \gamma +\delta +\mu )} \\ & -\beta\sqrt{\beta ^2 (\delta +\mu )^2+c^2 (\nu +\mu )^2 +2 \beta c (\nu +\mu ) (2 \gamma +\delta +\mu )} \\ & +c\beta (-2 \gamma -\delta +\nu ) -\beta^2 (\delta + \mu) -\beta c^2 (\nu +\mu ) \Bigr) \end{split}$$

\end{document}


Here are two possibilities (+ a variant), loading mathtools for themultlinedenvironment and thesplitfraccommand, andnccmath for its medium-size commands, combining them in various ways:

\documentclass{article}
\usepackage[showframe]{geometry}
\usepackage{mathtools, nccmath}

\begin{document} %

$$\begin{multlined}[b]i\to -\frac1{2 \beta ^2 c}\biggl[(-c \Bigl(\beta (-2 \gamma -\delta +\nu )+\sqrt{\beta ^2 (\delta +\mu )^2+c^2 (\nu +\mu )^2+2 \beta c (\nu +\mu ) (2 \gamma +\delta +\mu )}\Bigr) \\+\beta \Bigl(\beta \delta +\beta \mu +\sqrt{\beta ^2 (\delta +\mu )^2+c^2 (\nu +\mu )^2+2 \beta c (\nu +\mu ) (2 \gamma +\delta +\mu )}\Bigr)+c^2 (\nu +\mu )\biggr] \end{multlined}$$
\bigskip
\begin{aligned} i\to -\frac{\medmath{\splitfrac{-c \left(\beta (-2 \gamma -\delta +\nu )+\sqrt{\beta ^2 (\delta +\mu )^2+c^2 (\nu +\mu )^2+2 \beta c (\nu +\mu ) (2 \gamma +\delta +\mu )}\right) + }{\beta \left(\beta \delta +\beta \mu +\sqrt{\beta ^2 (\delta +\mu )^2+c^2 (\nu +\mu )^2+2 \beta c (\nu +\mu ) (2 \gamma +\delta +\mu )}\right)+c^2 (\nu +\mu )}}}{2 \beta ^2 c} \end{aligned}
\bigskip
\begin{aligned} i\to \medmath{-\frac{\splitfrac{-c \left(\beta (-2 \gamma -\delta +\nu )+\sqrt{\beta ^2 (\delta +\mu )^2+c^2 (\nu +\mu )^2+2 \beta c (\nu +\mu ) (2 \gamma +\delta +\mu )}\right) + }{\beta \left(\beta \delta +\beta \mu +\sqrt{\beta ^2 (\delta +\mu )^2+c^2 (\nu +\mu )^2+2 \beta c (\nu +\mu ) (2 \gamma +\delta +\mu )}\right)+c^2 (\nu +\mu )}}{2 \beta ^2 c}} \end{aligned}

\end{document}
`

• Thank you so much! This really helped me! With your comment I was able to solve my problem! – Isi Apr 23 '18 at 21:02