The velocity of a particle moving in space is \mathbf{v}(t)=e^{t} \mathbf{i}+4 t \mathbf{j}+\sin \pi t \mathbf{k} \text { Find the particle's position in terms of } t \text { if
} \mathbf{r}(0)=2 \mathbf{i}-\mathbf{j}+\frac{1}{\pi} \mathbf{k} \text {. }