import math

#function_x = lambda y: -math.cos(y - 2)
#function_y = lambda x: math.sin(x + 0.5) - 1

function_x = lambda x, y: math.sqrt(math.tan(x * y + 0.3))
function_y = lambda x: math.sqrt(abs(1.0 - 0.90 * x**2) / 2.0)

previous_x = 0
previous_y = 0
eps = 0.001
current_x = 1
current_y = 1

while (abs(previous_x - current_x) > eps and abs(previous_y - current_y) > eps):
    previous_y = current_y
    previous_x = current_x
    current_x = function_x (previous_x, previous_y)
    #current_x = function_x (previous_y)
    current_y = function_y (previous_x)
    print ("X =", current_x, "Y =", current_y)