import numpy as np
import matplotlib.pyplot as plt
import scipy.integrate as itg
def diff(y, t):
	return np.array([y[1], -y[0]])

t = np.linspace(0., 10., 101)
y = itg.odeint(diff, [1., 0.] , t)
plt.xlabel(r'$t$')
plt.plot(t, y[:, 0], '-', t, y[:, 1], '--')
plt.legend([r'$x$', r'$dx/dt$'], loc='best')
plt.show()