title: Drawing obtuse circular arc with arrowhead in matplotlib
body: <p>I am new to Python, though I do have previous programming experience. My current interest is to generate good quality schematics (and maybe later on also data graphs). </p>
  
  <p>I need to draw a circlar arc with an arrowhead at the end point. I have sieved through many posts and tried my hand at a few examples, but it seems I still miss some basic knowledge. So I need something like this:</p>
  
  <p><a href="http://i.stack.imgur.com/Z5V86.png">http://i.stack.imgur.com/Z5V86.png</a> </p>
  
  <p>I was experimenting with the example below, trying to initially plot a circular arc, but even this does not work. I am using matplotlib.patches but I am open to other suggestions for what I need.</p>
  
  <pre><code># -*- coding: utf-8 -*-
  import numpy as np
  import matplotlib.pyplot as plt
  from matplotlib.patches import Ellipse, Arc
  from matplotlib import cm, colors, patches
  from math import pi
  
  fig = plt.figure()
  ax = fig.add_subplot(1,1,1)
  ellipse = Arc([2.5,2.5],1,1,0,0,pi,color='green', linewidth='0.5')
  ax.add_patch(ellipse)
  plt.show()
  </code></pre>