ams math environment, missing $ in equation mode

Question

I'm trying to write some report in Latex, and I need to use amsmath further in the code, but since I added this package, the following piece of code stopped working (initially it was between \\[\\] instead of \begin{equation} and \end{equation}).

When I run my code, it stops on the following piece:

\begin{equation*} 
\text{d\overrightarrow{u} = } L \text{d\overrightarrow{x} with } L =\left( \begin{array}{ccc} 
\frac{\partial u_{1}}{\partial u_{1}} & \frac{\partial u_{1}}{\partial u_{2}} & \frac{\partial u_{1}}{\partial u_{3}} \\
\frac{\partial u_{2}}{\partial u_{1}} & \frac{\partial u_{2}}{\partial u_{2}} & \frac{\partial u_{2}}{\partial u_{3}} \\
\frac{\partial u_{3}}{\partial u_{1}} & \frac{\partial u_{3}}{\partial u_{2}} & \frac{\partial u_{3}}{\partial u_{3}} \end{array}\right) 
\end{equation*}

With the error:

Missing $ inserted. 

<inserted text>

               $

l.15 \text{d\overrightarrow{u} = }

                                   L \text{d\overrightarrow{x} with } L =\le..

?

I'd be grateful if I could get any help on this. If I missed a similar post, I'm really sorry for that, I checked around before posting.

Cheers JF

Answer 1

Apart from other design issues of this equation:

Using \text with mathematical macro contents requires to use \text{$\somemathmacro$}.

Some propositions for a better look

• \vec{u} looks better than \overrightarrow{u}, but \vv{u} from esvect does even look better (in my point of view), but not for a vector differential quantity.
• Perhaps L should be declared as math operator.
• \frac should possibly replaced by \dfrac

---

\documentclass{article}

\usepackage{mathtools}
\usepackage{esvect}
\begin{document}


\begin{equation*} 
\text{d$\overrightarrow{u}$} =  L \text{d$\overrightarrow{x}$ with }  L =\left( \begin{array}{ccc} 
\frac{\partial u_{1}}{\partial u_{1}} & \frac{\partial u_{1}}{\partial u_{2}} & \frac{\partial u_{1}}{\partial u_{3}} \\
\frac{\partial u_{2}}{\partial u_{1}} & \frac{\partial u_{2}}{\partial u_{2}} & \frac{\partial u_{2}}{\partial u_{3}} \\
\frac{\partial u_{3}}{\partial u_{1}} & \frac{\partial u_{3}}{\partial u_{2}} & \frac{\partial u_{3}}{\partial u_{3}} \end{array}\right) 
\end{equation*}


\begin{equation*} 
\text{d$\vec{u}$} =  L \text{d$\vec{x}$ with }  L =\left( \begin{array}{ccc} 
\frac{\partial u_{1}}{\partial u_{1}} & \frac{\partial u_{1}}{\partial u_{2}} & \frac{\partial u_{1}}{\partial u_{3}} \\
\frac{\partial u_{2}}{\partial u_{1}} & \frac{\partial u_{2}}{\partial u_{2}} & \frac{\partial u_{2}}{\partial u_{3}} \\
\frac{\partial u_{3}}{\partial u_{1}} & \frac{\partial u_{3}}{\partial u_{2}} & \frac{\partial u_{3}}{\partial u_{3}} \end{array}\right) 
\end{equation*}


%With \vv  macro from esvect.sty: 

\begin{equation*} 
\text{d$\vv{u}$} =  L \text{d$\vv{x}$ with }  L =\left( \begin{array}{ccc} 
\frac{\partial u_{1}}{\partial u_{1}} & \frac{\partial u_{1}}{\partial u_{2}} & \frac{\partial u_{1}}{\partial u_{3}} \\
\frac{\partial u_{2}}{\partial u_{1}} & \frac{\partial u_{2}}{\partial u_{2}} & \frac{\partial u_{2}}{\partial u_{3}} \\
\frac{\partial u_{3}}{\partial u_{1}} & \frac{\partial u_{3}}{\partial u_{2}} & \frac{\partial u_{3}}{\partial u_{3}} \end{array}\right) 
\end{equation*}


\end{document}

Answer 2

In your case it makes no sense to put math inside a \text{} command. I would do like the following (taking Manuel's comment and Stefan's answer into account):

% arara: pdflatex

\documentclass{article} 
\usepackage{mathtools}
\usepackage{cool}
\newcommand*\dd{\mathop{}\!\mathrm{d}}
\makeatletter
\renewcommand*\env@matrix[1][\arraystretch]{%
    \edef\arraystretch{#1}%
    \hskip -\arraycolsep
    \let\@ifnextchar\new@ifnextchar
    \array{*\c@MaxMatrixCols c}}
\makeatother

\begin{document}
\begin{equation*} 
    \mathrm{d}\vec{u} =  L\dd\vec{x} \text{ with } L = 
    \begin{pmatrix}[1.3]
    \pderiv{u_1}{u_1} & \pderiv{u_1}{u_2} & \pderiv{u_1}{u_3} \\
    \pderiv{u_2}{u_1} & \pderiv{u_2}{u_2} & \pderiv{u_2}{u_3} \\
    \pderiv{u_3}{u_1} & \pderiv{u_3}{u_2} & \pderiv{u_3}{u_3}
    \end{pmatrix}
\end{equation*}
\end{document}