\( \definecolor{colordef}{RGB}{249,49,84} \definecolor{colorprop}{RGB}{18,102,241} \)
Find the matrix representing a rotation of \(\frac{\pi}{2}\) radians anti-clockwise about the origin.
$$ \mathbf{R} = \begin{pmatrix}\input{145099}{}{3em}{2em}{}{} & \input{245099}{}{3em}{2em}{}{}\\ \input{345099}{}{3em}{2em}{}{} & \input{445099}{}{3em}{2em}{}{}\\ \end{pmatrix}$$