import math


def coordinates_on_circle(n):
    """Returns x,y coordinates of points on an unit circle with spacing 2π/n"""
    if type(n)!=int:
        raise Exception("Wrong input: \n the argument must be an integer number of points on the unit circle!")
    x,y = [],[]
    step_angle = 2*math.pi/n
    for i in range(0,n):
        x.insert(len(x),math.cos(i*step_angle))
        y.insert(len(y),math.sin(i*step_angle))
    return x,y