def unit_vector(v):
    """Return the unit vector of the points
       v = (a,b)"""
    h = ((v[0]**2)+(v[1]**2))**0.5
    if h == 0:
        h = 0.000000000000001
    ua = v[0] / h
    ub = v[1] / h
    return (ua, ub)