import numpy as np
import matplotlib.pyplot as plt

nbx = 101
x = np.linspace(0, 10, nbx)
y = np.cos(x)
h = x[1]-x[0] # calcul du pas

# calcul des valeurs de la dérivée
yp = (y[1:] - y[:-1]) / h
    
plt.plot(x, y, label="f(x)")
plt.plot(x[:-1], yp, label="f'(x)")

plt.legend()
plt.show()