Added plot of tanh

Author: mnielsen

fig/chap3/tanh.png

@@ -0,0 +1,22 @@
+"""
+tanh
+~~~~
+
+Plots a graph of the tanh function."""
+
+import numpy as np
+import matplotlib.pyplot as plt
+
+z = np.arange(-5, 5, .1)
+t = np.tanh(z)
+
+fig = plt.figure()
+ax = fig.add_subplot(111)
+ax.plot(z, t)
+ax.set_ylim([-1.0, 1.0])
+ax.set_xlim([-5,5])
+ax.grid(True)
+ax.set_xlabel('z')
+ax.set_title('tanh function')
+
+plt.show()