Question:
If $A$ is a square matrix, then $A A$ is a
(a) skew-symmetric matrix
(b) symmetric matrix
(c) diagonal matrix
(d) none of these
Solution:
(d) none of these
Given: A is a square matrix.
Let $A=\left[\begin{array}{ll}1 & 2 \\ 1 & 0\end{array}\right]$
$\Rightarrow A A=\left[\begin{array}{ll}1 & 2 \\ 1 & 0\end{array}\right]\left[\begin{array}{ll}1 & 2 \\ 1 & 0\end{array}\right]=\left[\begin{array}{ll}3 & 2 \\ 1 & 2\end{array}\right]$