# Hiermee bereken je de parameters in het geval dat D < 0

import numpy as np

E = 0.9
J = 5
Rs = 1

K = E
U = 1 - K**2

a = Rs
b = -1
c = Rs / J**2
d = - U / J**2

D = 18 * a * b * c * d - 4 * a * c**3 - 27 * a**2 * d**2 + b**2 * c**2 - 4 * b**3 * d

n1a = 1 / (3 * Rs)
n1b = 1 / (27 * Rs**3) + 1 / (3 * Rs * J**2) - E**2 / (2 * Rs * J**2)
n1c = np.sqrt (E**4 / (4 * Rs**2 * J**4) - E**2 / (3 * Rs**2 * J**4) - E**2 / (27 * Rs**4 * J**2) \
 + 1 / (27 * J**6) + 2 / (27 * Rs**2 * J**4) + 1 / (27 * Rs**4 * J**2))
n1d = n1b + n1c
n1e = n1b - n1c

if n1d < 0:
 n1d = - (- n1d)**(1/3)
else:
 n1d = n1d**(1/3)

if n1e < 0:
 n1e = - (- n1e)**(1/3)
else:
 n1e = n1e**(1/3)

n1 = n1a + n1d + n1e
r1 = 1 / n1

print ("J = ", J)
print ("Rs = ", Rs)
print ("E = ", E)
print ("K = ", K)
print ("U = ", U)
print ("a = ", a)
print ("b = ", b)
print ("c = ", c)
print ("d = ", d)
print ("D = ", D)
print ("n1 = ", n1)
print ("r1 = ", r1)