title: Draw ellipse in matplotlib given the focii
body: <p>The equation of an ellipse is:</p>
  
  <pre><code>sqrt((x-a1)**2 + (y-b1)**2) + np.sqrt((x-a2)**2 + (y-b2)**2) = c
  </code></pre>
  
  <p>The focii are <code>(a1, b1)</code> and <code>(a2, b2)</code>. <code>c</code> is also known. How do I draw this in python using matplotlib?</p>
  
  <p>Thanks for your help.</p>