Trace of 2X2 Matrix

[Math | Numerical Analysis | Matrices] This equation computes the trace of a two-by-two matrix.  Given a square matrix where

A = `[[A_11,A_12],[A_21,A_22]]`,

The Trace of this matrix is defined as tr (A) = `A_11` + `A_22`

The trace can be used in a number of numerical analyses computing things like the eigenvalues of a matrix.

Notes

The trace of a square matrix (the matrix must be a square matrix) is simply the sum of the diagonals: `A_11 + A_22 +` ... `A_nn`.

Note that the trace of a matrix is equal to that of its transpose, i.e., tr(A) = tr(A^T)