Question

Which of the following is a diagonal matrix?

Answer 1

A square matrix is diagonal if and only if it is triangular and normal. Any square diagonal matrix is also a symmetric matrix. A symmetric diagonal matrix can be defined as a matrix that is both upper- and lower-triangular. The identity matrix In and any square zero matrix are diagonal.

Answer 2

A square matrix having all its elements except in the leading ( principal) diagonal are zero is called a diagonal matrix.