title: Why does np.arccos(1.0) give nan if fed by np.arange?
body: <p>Can anyone replicate this?</p>
  
  <pre><code>import numpy as np
  print np.arccos(1.0)
  print np.arccos(1)
  for x in np.arange(0.7,1,0.05):
      print x
      print np.arccos(x)
  </code></pre>
  
  <p>Output:</p>
  
  <pre><code>0.0
  0.0
  0.7
  0.795398830184
  0.75
  0.722734247813
  0.8
  0.643501108793
  0.85
  0.55481103298
  0.9
  0.451026811796
  0.95
  0.317560429292
  1.0
  nan
  </code></pre>
  
  <p>Note the last value,which should be <code>np.arccos(1.0)</code>, is <code>nan</code>. When I do <code>np.arccos(1.0)</code> in the console it is <code>0.0</code> as I would expect. What is causing this behaviour?</p>
  
  <p>Note, I am using Python 2.7.6 Spyder IDE Win7</p>