The equation is too long to fit in the page. Is it possible to break it without using package amsmath? Does anyone know how to solve this ;
\documentclass{article}
\usepackage[utf8]{inputenc}
\title{FEM assignment}
\author{El & Cauist}
\date
\begin{document}
\maketitle \
\begin{equation} \label{eq:1}
-(\textbf{\tilde{\nabla}_1}-\textbf{\tilde{\nabla}_0})^T[r\textbf{D}(\textbf{\tilde{\nabla}_1}+\textbf{\tilde{\nabla}_0})\textbf{u}]=r \textbf{b} \end{equation}

amsmathpackage? – Mico Jan 30 '18 at 18:19\begin{eqnarray}...\end{eqnarray}environment. (I almost do not dare to say it loud, but this has even some advantages, e.g. it works with\pausefrom the beamer package. But it also has disadvantages.) – Jan 30 '18 at 18:21\title{FEM assignment} \author{El & Cauist} \date
\begin{document}
\maketitle
\
\begin{equation} \label{eq:1} -(\textbf{\tilde{\nabla}_1}-\textbf{\tilde{\nabla}_0})^T[r\textbf{D}(\textbf{\tilde{\nabla}_1}+\textbf{\tilde{\nabla}_0})\textbf{u}]=r \textbf{b} \end{equation}
– Ellev Jan 30 '18 at 18:26\author{El \& Cauist}instead of\author{El & Cauist}? – Jan 30 '18 at 18:40\date{}. Do not use\textbf{}in math mode. – Sigur Jan 30 '18 at 18:43\tildeis that it requires math mode, and you are using it within\textbfwhich resets the node to text mode. if you use\mathbfinstead, there should be no error reported. – barbara beeton Jan 30 '18 at 19:05