The position vectors of the points \(A\) and \(B\), relative to a fixed origin \(O\), are given by
$$\mathbf{a} = -3\mathbf{i} + 4\mathbf{j}, \quad \mathbf{b} = 5\mathbf{i} + 8\mathbf{j},$$
respectively.
- Find the vector \(\overrightarrow{AB}\). [2]
- Find a unit vector in the direction of \(\mathbf{a}\). [2]
- The point \(C\) is such that the vector \(\overrightarrow{OC}\) is in the direction of \(\mathbf{a}\). Given that the length of \(\overrightarrow{OC}\) is 7 units, write down the position vector of \(C\). [1]
- Calculate the angle \(AOB\). [3]