Diagonal Matrix
 A diagonal matrix is an n x n matrix with every off diagonal element equal to zero.
 This is often written showing just the diagonal elements and the upperright and lowerleft corners with a 0

 If we have two matrices such that:

 Then:
 If each element , then
 The eigenvalues of D are its main diagonal elements, d_{1}, d_{2}, d_{3}, ......d_{n}
See also: Hankel Matrix, Matrix, Trace.
Subjects: Mathematics
 Further reading:
 Matrices: Theory and Applications (Graduate Texts in Mathematics), , SpringerVerlag Berlin and Heidelberg GmbH & Co. KG