9 The equation of a straight line \(l\) is \(\mathbf { r } = \left( \begin{array} { l } 3
1
1 \end{array} \right) + t \left( \begin{array} { r } 1
- 1
2 \end{array} \right) . O\) is the origin.
- The point \(P\) on \(l\) is given by \(t = 1\). Calculate the acute angle between \(O P\) and \(l\).
- Find the position vector of the point \(Q\) on \(l\) such that \(O Q\) is perpendicular to \(l\).
- Find the length of \(O Q\).