# Bad math environment delimiter when using \begin{split} and \end{split}

I have the following equation in Texmaker:

$$\begin{split} f_{2}(\tau)I_{\theta}(\tau)|_{W_{2}} & = \frac{8\dot{a}c\lambda \e^{2\tau} (\lambda^{2}-\e^{2\tau})}{v_{0}(\e^{2\tau}+\lambda^{3})(\e^{2\tau} + \lambda^{2})}\left(-\frac{2a\lambda (\(\e^{2\tau}+\lambda)}{(\e^{2\tau}+\lambda^{2})(\e^{2\tau}+1)} - \frac{a(\lambda+1)}{(\e^{2\tau}+1)} + \frac{2c\lambda(\lambda^{2}-\e^{2\tau})}{(\e^{2\tau}+\lambda^{2})(\e^{2\tau}+\lambda)}\right) \\ & + \frac{16\dot{b}a c \lambda^{2} \e^{2\tau}}{vb(\e^{2\tau} + \lambda^{3})(\e^{2\tau} + \lambda^{2})} \left( \frac{(\lambda^{2} - \e^{2\tau})(\e^{2\tau} + \lambda)}{(\e^{2\tau} + 1)(\e^{2\tau} + \lambda^{2})} + \frac{(\lambda - \e^{2\tau})}{\e^{2\tau} + 1} + \frac{4c \lambda^{2} \e^{2\tau}}{a(\e^{2\tau} + \lambda)(\e^{2\tau} + \lambda^{2})} \right) \label{f2Ithetamod} \end{split}$$


When I compile, I get the error message " LaTeX Error: Bad math environment delimiter." However the PDF file produced is fine.

How do I correct this error? Thanks.

• It looks like your code contains a typo, a \( that should probably be a (, in the first line, where it says \left(-\frac{2a\lambda (\(\e^{2\tau}+\lambda)} etc. – GuM May 31 '17 at 0:04

Here is a solution, with multlined from mathtools and fleqn from nccmath (the analog of the fleqn option, but for a single group of equations), combined with geometry, to have sensible outer margins (this supposes you don't use too wide margin notes):

\documentclass{article}

\usepackage{mathtools, nccmath}
\usepackage{geometry}
\newcommand\e{\mathrm e}
\usepackage{showframe}
\renewcommand\ShowFrameLinethickness{0.3pt}

\begin{document}

\begin{fleqn}[2em]
$$\begin{multlined} f_{2}(\tau)I_{\theta}(\tau)\mid{W_{2}} =\\ \frac{8\dot{a}c\lambda \e^{2\tau} (\lambda^{2}-\e^{2\tau})}{v_{0}(\e^{2\tau}+\lambda^{3})(\e^{2\tau} + \lambda^{2})}% \left(-\frac{2a\lambda ((\e^{2\tau}+\lambda)}{(\e^{2\tau}+\lambda^{2})(\e^{2\tau}+1)} - \frac{a(\lambda+1)}{(\e^{2\tau}+1)} + \frac{2c\lambda(\lambda^{2}-\e^{2\tau})}{(\e^{2\tau}+\lambda^{2})(\e^{2\tau}+\lambda)}\right) \\% + \frac{16\dot{b}a c \lambda^{2} \e^{2\tau}}{vb(\e^{2\tau} + \lambda^{3})(\e^{2\tau} + \lambda^{2})} \left( \frac{(\lambda^{2} - \e^{2\tau})(\e^{2\tau} + \lambda)}{(\e^{2\tau} + 1)(\e^{2\tau} + \lambda^{2})} + \frac{(\lambda - \e^{2\tau})}{\e^{2\tau} + 1} + \frac{4c \lambda^{2} \e^{2\tau}}{a(\e^{2\tau} + \lambda)(\e^{2\tau} + \lambda^{2})} \right) \label{f2Ithetamod} \end{multlined}$$
\end{fleqn}

\end{document}