Give an anticlockwise parametrization \( \mathbf{r}(t) \) of the arc pictured below beginning at \( t=0 \) and ending at \( t=\frac{\pi}{2} \)
Give your answer as a vector function, with square brackets \( [x(t), y(t)] \).
(Be careful NOT to use an interval from the palette.)
\[
\mathbf{r}(t)=\quad t \in\left[0, \frac{\pi}{2}\right]
\]