PlanetPhysics/Example of Trace

For the matrix $$M,$$

$$ M = \left( \begin{matrix} 8 & 1 & 6 \\ 3 & 5 & 7 \\ 4 & 9 & 2 \end{matrix} \right) $$

the trace of $$M,$$ $$tr(M)$$ is

$$ tr(M) = 8 + 5 + 2 = 15 $$