From part a),
\displaystyle \mathbf{v}=2\textrm{.}5\mathbf{i}+4\mathbf{j} which gives,
\displaystyle \begin{align} & \tan \alpha =\frac{4}{2\textrm{.}5} \\ & \alpha =58\textrm{.}0{}^\circ \\ \end{align}
