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<A NAME=TRACE>

<TITLE>TRACE</TITLE></A>
<b><a href=r37_idx.html>INDEX</a></b><p><p>



<B>TRACE</B> _ _ _  _ _ _  _ _ _  _ _ _ <B>operator</B><P>
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The <em>trace</em> operator finds the trace of its 
<A HREF=r37_0345.html>matrix</A> argument. 
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syntax: </H3>
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<em>trace</em>(&lt;expression&gt;) or <em>trace</em> &lt;simple\_expression&gt; 

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&lt;expression&gt; or &lt;simple\_expression&gt; must evaluate to a square 
matrix. 
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 <P> <H3> 
examples: </H3>
<P><PRE><TT>
matrix a; 

a := mat((x1,y1),(x2,y2))$ 

trace a; 

  X1 + Y2

</TT></PRE><P>The trace is the sum of the entries along the diagonal of a square
 matrix. 
Given a non-matrix expression, or a non-square matrix, <em>trace</em> returns 
an error message. 
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