[Tex/LaTex] ! Package amsmath Error: \begin{split} won’t work here

amsmathequationssplittexmaker

I tried to run following code in texmaker,

\begin{equation} \label{eq4}  
\begin{split}  
&R^T \left( \underbar r_{H/G} \times \underline f_H + \underline r_{R/G} \times \underline f_R + \underline \tau_R \right) \\  
 &= I_G \underline \alpha + \underline \omega \times \left( I_G \underline \omega \right)  
\end{split}  
\end{equation}

and got following error message,

! Package amsmath Error: \begin{split} won't work here.

What caused this problem and how can I fix it?

Of course, this is part of a document. Therefore, \begin{document} and \end{document} exist at the beginning and the end of the document.

Edited:

@daleif

\documentclass[fleqn,10pt,twocolumn]{ICCAS2020}

\usepackage{lipsum} 
\usepackage {subfigure}
\usepackage[T1]{fontenc}
\usepackage[sc]{mathpazo}
\usepackage{cite}
\usepackage {amsmath}
\usepackage{graphicx}
\usepackage[english]{babel}
\usepackage{mathtools}

\begin{document}

\section{EX}

\begin{equation} \label{eq4}
\begin{split}
&R^T \left( \underbar r_{H/G} \times \underline f_H + \underline r_{R/G} \times \underline f_R + \underline \tau_R \right) \\
 &= I_G \underline \alpha + \underline \omega \times \left( I_G \underline \omega \right)
\end{split}
\end{equation}

\end{document}

Is this what you mean?

@Sebastiano

Thanks for your kind welcome, but your code didn't work for me.

By the way, what does MWE mean?

Best Answer

Remove the fleqn option. The class you use essentially do something like this when the fleqn option is active

\usepackage{amsmath}
\input{fleqn.clo}

So if we try

\documentclass{article}
\usepackage{amsmath}
\makeatletter
\input{fleqn.clo}
\makeatother
\begin{document}
\begin{equation} \label{eq4}
\begin{split}
&R^T \left( \underbar r_{H/G} \times \underline f_H + \underline r_{R/G} \times \underline f_R + \underline \tau_R \right) \\
 &= I_G \underline \alpha + \underline \omega \times \left( I_G \underline \omega \right)
\end{split}
\end{equation}
\end{document}

we get the same error, which goes away if the \input line is removed.

I'd recommend writing to the organisers and showing them your example.

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