title: Numpy - square root of -1 leaves a small real part
body: <p>Perhaps this is an algorithmic issue, but the following piece of code</p>
  
  <p><code>numpy.power((-1+0j),0.5)</code></p>
  
  <p>produces the following output</p>
  
  <p><code>(6.1230317691118863e-17+1j)</code></p>
  
  <p>Analogous expressions e.g. <code>numpy.power(complex(-1),.5)</code> yield the same result, however - <code>numpy.sqrt(complex(-1))</code> yields the expected result of <code>1j</code>. Clearly the result should have no real part, so I am missing something crucial or do I need to report this to numpy dev's.</p>
  
  <p>In case anyone asks, no I can not round away the real part (I need full precision for this calculation) and yes I need to use the power function.</p>