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# If matrix A = (1,2,3), write AA' where A' is the transpose of matrix A.

Toolbox:
• If A_{i,j} be a matrix m*n matrix , then the matrix obtained by interchanging the rows and column of A is called as transpose of A.
• If A is an m-by-n matrix and B is an n-by-p matrix, then their matrix product AB is the m-by-p matrix whose entries are given by dot product of the corresponding row of A and the corresponding column of B: $\begin{bmatrix}AB\end{bmatrix}_{i,j} = A_{i,1}B_{1,j} + A_{i,2}B_{2,j} + A_{i,3}B_{3,j} ... A_{i,n}B_{n,j}$
Given:
$A=\begin{bmatrix}1 &2 & 3\end{bmatrix}$
Transpose of a matrix can be obtained by changing the rows and the column.
$A'=\begin{bmatrix}1 \\2 \\ 3\end{bmatrix}$
$AA'=\begin{bmatrix}1 &2 & 3\end{bmatrix}\begin{bmatrix}1\\2\\3\end{bmatrix}$
$\Rightarrow [1(1)+2(2)+3(3)]$
$\Rightarrow [1+4+9]$=14
Hence AA'=14.