The Trace(A) function computes the sum of the diagonal elements of Matrix A.

This function is part of the LinearAlgebra package, and so it can be used in the form Trace(..) only after executing the command with(LinearAlgebra). However, it can always be accessed through the long form of the command by using LinearAlgebra[Trace](..).

$\mathrm{with}\left(\mathrm{LinearAlgebra}\right)\:$

$A≔⟨⟨a\,b\,c⟩\left|⟨d\,e\,f⟩\right|⟨g\,h\,i⟩⟩$

$A≔\left[\begin{array}{ccc}a& d& g\\ b& e& h\\ c& f& i\end{array}\right]$

$\mathrm{Trace}\left(A\right)$

$a+e+i$