Define trace of a matrix and find the trace of $\left[\begin{array}{ccc}1& 2& -1/2\\ 0& -1& 2\\ -1/2& 2& 1\end{array}\right]$

Trace of a matrix : The sum of the elements of the principal diagonal of a square matrix is called trace of matrix

Let $A=\left[\begin{array}{ccc}1& 2& -1/2\\ 0& -1& 2\\ -1/2& 2& 1\end{array}\right]$

Then $\mathrm{tr}\left(A\right)=1+(-1)+1=1$