Question

A sqare matrix $A{\left[a_{ij}\right]}_{{}_{{}_{n\times n}}}$ 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)

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