The velocity is the first derivative of the position vector $\mathbf{r}(t)$. So, we differentiate $\mathbf{r}(t)$ with respect to $t$ to get the velocity vector $\mathbf{v}(t)$:
\[\mathbf{v}(t) = \frac{d\mathbf{r}}{dt} = -2\sin t \mathbf{i} - 3\cos t \mathbf{j}\]
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