errorsfont-encodingsinput-encodings
Why do I get an "ERROR: Please use \mathaccent for accents in math mode." for the following code?
\[c=439 450\times10^6\frac{\mathrm{millimètre}}{\mathrm{seconde}}\]
I am guessing \usepackage[utf8]{inputenc} is having problems with the accented "è" in "millimètre."
I managed to fix this on my own.
The problem was that my .tex file used utf-8 encoding, but my .bib file used ANSI-encoding. The error presented itself, when I added a bibliography entry which contained an apostrophe. To fix this I converted the .bib file to utf-8 encoding with Notepad++ and removed the files produced by pdflatex (aux, .bbl, .bcf etc.) and then ran pdflatex again.
This redefines it for math mode only, retaining its original use in text mode. EDITED , per egreg's recommendation, to use \DeclareRobustCommand in lieu of \def. The \expandafter in the definition allows the following \fi to be absorbed, so that the text version of \c can operate on the actual argument that follows.
\documentclass{book}
\let\svc\c
\DeclareRobustCommand\c{\ifmmode\mathrm{c}\else\expandafter\svc\fi}
\begin{document}
This is a \c complicated test.
Complement of $A$: $A^\c$.
\end{document}
Best Answer
It works fine when you use
\textinstead of\mathrm.\textis part ofamsmath, which is loaded bymathtools…\mathrmwon’t create real text, it only changes the math alphabet from italics to recto. But in the math alphabet there are no accent characters likeè…