Question

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

• A. i = j
• B. i < j
• C. i > j
• D. none of these

Answer 1

Answer: (B)

i < j

Answer 2

$A = [a_{ij}]_{n \times n}$ is lower triangular iff all entries above the diagonal vanish, i.e., if $a_{ij} = 0$ for $i < j$.