Question

A square matrix $A=[a_{ij}{]}_{n\times n}$ is called a diagonal matrix if $a_{ij}=0$ for

• A. i = j
• B. i < j
• C. i > j
• D. i $\ne$ j

Answer 1

Answer: (D)

$A=[a_{ij}{]}_{n\times n}$ is a diagonal matrix iff all non-diagonal entries are 0, i.e., iff $a_{ij}=0$ for $i\ne j$.