Two dimensional coordinates can be rotated by my multiplying the 2-element vector of coordinates by 2x2 rotation matrix
where θ is the angle of rotation (in radians). Start from the x-y coordinates
in the file points_circle.dat and rotate them by 90°. Utilize broadcasting for
performing the rotation with a single np.dot call. (Hint: you may need to
create additional dimensions). Plot both the original and rotated points in
order to see the effect of rotation.