I am writing an equation in LYX and I get the error "Undefined control sequence" With the message
"The control sequence at the end of the top line of your error message was never \def'ed. If you have misspelled it (e.g.,
\hobx'), type
I' and the correct spelling (e.g., `I\hbox'). Otherwise just continue, and I'll forget about whatever was undefined."
\batchmode
\makeatletter
\def\input@path{{C://Desktop}}
\makeatother
\documentclass[english]{book}
\renewcommand{\familydefault}{\rmdefault}
\usepackage[T1]{fontenc}
\usepackage[latin9]{inputenc}
\usepackage{geometry}
\geometry{verbose,tmargin=1.5cm,bmargin=2.5cm,lmargin=2.5cm,rmargin=2.5cm}
\setcounter{secnumdepth}{3}
\setcounter{tocdepth}{3}
\usepackage{setspace}
\doublespacing
\usepackage{babel}
\begin{document}
\begin{equation}
c=\alpha+\beta[\frac{1}{\varOmega}\int_{\varOmega}\frac{|\nabla\rho(r)|} {\rho(r)}dr]^{1/2}
\end{equation}
\end{document}
How to correct that?
{
, stray empty lines, missing/extra&
or `\\`). – vonbrand Dec 25 '15 at 15:58