Question

Identify the non-diagonal matrix from the given options.

• A. $\left[\begin{array}{ccc}1& 0& 0\\ 0& 1& 0\\ 0& 0& 1\end{array}\right]$
• B. $\left[\begin{array}{ccc}1& 0& 0\\ 0& 2& 0\\ 1& 9& 0\end{array}\right]$
• C. $\left[\begin{array}{ccc}1& 0& 0\\ 0& 4& 0\\ 0& 0& 1\end{array}\right]$
• D. $\left[\begin{array}{ccc}1& 0& 0\\ 0& 4& 0\\ 0& 0& -1\end{array}\right]$

Answer 1

The correct option is B $\left[\begin{array}{ccc}1& 0& 0\\ 0& 2& 0\\ 1& 9& 0\end{array}\right]$

A diagonal matrix is defined as a square matrix which has all its diagonal elements as non-zero, and all the non-diagonal elements as zero.

Thus, option $A,C,D$ satisfy the definition, while option $B$ does not.