# How to represent the trace of a matrix [duplicate]

Possible Duplicate:
Define additional math operators to be typeset in roman

The trace of a matrix is often written as "Tr [matrix] ", but there does not seem to be a naive LaTeX symbol for this.

The trace is defined as the sum on the main diagonal.

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## marked as duplicate by Andrey Vihrov, dmckee, egreg, Mico, cmhughesNov 12 '11 at 0:04

Do you mean \DeclareMathOperator{\Tr}{Tr}? – Andrey Vihrov Nov 11 '11 at 23:17
@AndreyVihrov Yeah. I think I do. – dmckee Nov 11 '11 at 23:18

\usepackage{amsmath}

The \mathrm is automatically issued by \DeclareMathOperator. – egreg Nov 11 '11 at 23:23