import math


def circunference_line(x, r, xp1=0, yp1=0):
    """
    Calculating the coordinates of a point on a circles
    circumference from the radius, an origin and the 
    arc between the points
    """
    xp2 = xp1 + r * math.sin(x)
    yp2 = yp1 - r * (1- math.cos(x) )   
    #try:
    #    xp2 = xp1 + r * math.cos(math.tau/x)
    #    yp2 = yp1 + r * math.sin(math.tau/x)
    #except ZeroDivisionError:
    #    xp2 = x 
    #    yp2 = yp1       
    return xp2, yp2