Let \({a} = \begin{pmatrix} 2 \\ -6 \\ 5 \end{pmatrix} \quad \text{and} \quad {b} = \begin{pmatrix} -1 \\ -2 \\ 0 \end{pmatrix}.\) Let \(\theta\) be the angle between \({a}\) and \(b\). Find \(\cos^2 \theta\).
cos^2 (theta) = 9/13.
