Question

If matrix A = [1 2 3], write AA^T.

Answer 1

$$\begin{gathered} \mathrm{Given}:A=\left[\begin{array}{ccc}1& 2& 3\end{array}\right] \\ {A}^T=\left[\begin{array}{c}1\\ 2\\ 3\end{array}\right] \\ A{A}^T=\left[\begin{array}{ccc}1& 2& 3\end{array}\right]\left[\begin{array}{c}1\\ 2\\ 3\end{array}\right] \\ \Rightarrow A{A}^T=1+4+9 \\ \Rightarrow A{A}^T=14 \end{gathered}$$