(a) Briefly describe how you would check that the curve transformation works properly.
(b) Write your definition of Curve-Transform reflect_through_y_axis.

def rotate_90(curve):
    def rotated_curve(t):
        pt = curve(t)
        return make_point(-y_of(pt), x_of(pt))
    return rotated_curve

def reflect_through_y_axis(curve):
    def reflected_curve(t):
    ? ? ? ? ?
    return reflected_curve