import matplotlib.pyplot as plt
import numpy as np
a1=0.5
a2=0.5
b1=0.2
b2=0.1
ax = plt.axes()
ax.arrow(0, 0, a1, a2, head_width=0.05, head_length=0.05, fc='k', ec='k')
ax.arrow(0, 0, b1, b2, head_width=0.05, head_length=0.05, fc='k', ec='k')
ax.arrow(0, 0, a1+b1,a2+b2, head_width=0.05, head_length=0.1, fc='r', ec='k')
#print(np.sqrt(9))
plt.show()