(a)[2]
Express $\frac{s}{t}$ as $re^{i\theta}$ where $-\pi < \theta \leq \pi$ and $r > 0$.
(b)[2]
On an Argand diagram with origin $O$, the points $A$ and $B$ stand for the complex numbers $s$ and $\frac{s}{t}$ respectively. By looking at the line segments $OA$ and $OB$, or in another way, State the two geometric effects of dividing a complex number by $6e^{3i}$.