Hello, I wrote this code to visualize the solution of a differential equation, but I observed that a change happens in the the ordinate’s amplitude in the abscissa 0 if I increased the length of the abscissa from 200 to 400

Please, Is what happened a problem? If yes, how can I fix it?

CODE :

from numpy import *

from matplotlib.pyplot import *

from scipy.integrate import odeint

k = 284*10**5
w0 = 512.8
F0 = 131
𝝃 = 0.05
m = 108
c = 2*𝝃

*w0*m

β = 0.1

w = 0.01

def F(Y,t) :

Zzero, Zun = Y[0], Y[1]

return array([ Zun, (1/m)

*(-k*Zzero-c

*Zun+F0*cos(w

*t)-β*Zzero**3)])

vi = [0, 0]

t1 = linspace(0 ,200, 100000)

t2 = linspace(0 ,400, 100000)

solution1 = odeint(F, vi, t1)

solution2 = odeint(F, vi, t2)

Z01 = solution1 [ :, 0]

Z02 = solution2 [ :, 0]

subplot(211)

plot(t1, Z01, label = “Cote”)

legend()

xlabel(" Temps (s)")

ylabel(“Déplacement1 (m)”)

grid(True)

rcParams[‘figure.figsize’] = [15, 8]

subplot(212)

plot(t2, Z02, label = “Cote”)

legend()

xlabel(" Temps (s)")

ylabel(“Déplacement2 (m)”)

grid(True)

rcParams[‘figure.figsize’] = [15, 8]

show()

Thank you and good day.