9 Relative to an origin \(O\), the position vectors of the points \(A , B\) and \(C\) are given by
$$\overrightarrow { O A } = \left( \begin{array} { r }
2
3
- 6
\end{array} \right) , \quad \overrightarrow { O B } = \left( \begin{array} { r }
0
- 6
8
\end{array} \right) \quad \text { and } \quad \overrightarrow { O C } = \left( \begin{array} { r }
- 2
5
- 2
\end{array} \right)$$
- Find angle \(A O B\).
- Find the vector which is in the same direction as \(\overrightarrow { A C }\) and has magnitude 30 .
- Find the value of the constant \(p\) for which \(\overrightarrow { O A } + p \overrightarrow { O B }\) is perpendicular to \(\overrightarrow { O C }\).