# How to change specific symbols in math mode

I use \usepackage[utopia]{mathdesign} for math numbers, symbols, etc. but I want to change the \sum symbol to default computer modern one. When I use

\DeclareSymbolFont{CMlargesymbols}{OMX}{cmex}{m}{n}
\DeclareMathSymbol{\‎‏‎sum‎}{\mathop}{CMlargesymbols}{"50}‎‎‎


it results an error: Command '\sum' already defined. How can I change the \sum symbol?

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Try "undefining" it first via \let\sum\relax before your \DeclareMathSymbol definition. – Werner Dec 7 '12 at 18:27
– Werner Dec 7 '12 at 18:28
I get no error. Please, add a minimal working example (MWE). The two commands about \sum should go after loading mathdesign. – egreg Dec 7 '12 at 18:50
@egreg the cause of this error is calling amsmath package. but i don't know why this happens? – smh Dec 8 '12 at 11:15

\documentclass{article}

\usepackage[utopia]{mathdesign}

\DeclareSymbolFont{CMlargesymbols}{OMX}{cmex}{m}{n}
\DeclareMathSymbol{\sum}{\mathop}{CMlargesymbols}{"50}

\usepackage{amsmath}

\begin{document}

$\sum$

\end{document}


This is because amsmath patches some of the commands to become "dots-aware".

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\DeclareMathSymbol{\mysum}{\mathop}{CMlargesymbols}{"50}

\renewcommand{\sum}{\mysum}