X = np.linspace(-2 * np.pi, 2 * np.pi, 70, endpoint=True)
F1 = np.sin(X)
F2 = 3 * np.sin(X)
ax = gca()
ax.spines['top'].set_color('none')
ax.spines['right'].set_color('none')
ax.xaxis.set_ticks_position('bottom')
ax.spines['bottom'].set_position(('data',0))
ax.yaxis.set_ticks_position('left')
ax.spines['left'].set_position(('data',0))
xticks( [-6.28, -3.14, 3.14, 6.28],
[r'$-2\pi$', r'$-\pi$', r'$+\pi$', r'$+2\pi$'])
yticks([-3, -1, 0, +1, 3])
for t in ax.get_xticklabels():
t.set_fontsize(18)
t.set_bbox(dict(facecolor='white', edgecolor='None', alpha=0.7))
for t in ax.get_yticklabels():
t.set_fontsize(14)
t.set_bbox(dict(facecolor='white', edgecolor='None', alpha=0.7))
plot(X, F1, label="$sin(x)$")
plot(X, F2, label="$3 sin(x)$")
legend(loc='lower left')
show()