If \( A = \begin{bmatrix} \alpha & 3 & 1 2 & \beta & 6 -2 & -1 & \gamma \end{bmatrix} \) and \( AA^T = \begin{bmatrix} 35 & 28 & -13 28 & 56 & -8 -13 & -8 & 5 \end{bmatrix} \), then Trace of \( A = \)
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In \( AA^T \), the diagonal entry \( d_i \) is always the square of the norm of the \( i \)-th row vector. Use this to find absolute values of unknowns quickly, then use one off-diagonal entry to fix the signs.