<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def rotate_2D(angle):
 """ Returns a 2x2 transformation matrix to rotate by an angle in two dimensions """

    return N.array([[N.cos(angle),-N.sin(angle)],
                    [N.sin(angle),N.cos(angle)]])