Question

Which of the following is a diagonal matrix?

Answer 1

A matrix is diagonal if

$i\neq j \implies A_{i,j}=0$

In other words, you want non-zero elements only when the indices of the row and the column are the same: the first element of the first row must be non zero, the second element of the second row must be non-zero, and so on. All other elements must be zero.

Answer 2

Answer:

Option 3

Step-by-step explanation: