Question

If A is a square matrix, then AA is a
(a) skew-symmetric matrix
(b) symmetric matrix
(c) diagonal matrix
(d) none of these

Answer 1

(d) none of these

Given: A is a square matrix.

$$\begin{gathered} \mathrm{Let}A=\left[\begin{array}{cc}1& 2\\ 1& 0\end{array}\right] \\ \Rightarrow AA=\left[\begin{array}{cc}1& 2\\ 1& 0\end{array}\right]\left[\begin{array}{cc}1& 2\\ 1& 0\end{array}\right]=\left[\begin{array}{cc}3& 2\\ 1& 2\end{array}\right] \end{gathered}$$