title: I'm getting an error <string>:149: RuntimeWarning: invalid value encountered in sqrt while generating a list
body: <pre><code>def ellipse(numPoints, genX=np.linspace, HALF_WIDTH=10, HALF_HEIGHT=6.5):
      xs = 10.*genX(-1,1,numPoints)
      ys = 6.5*np.sqrt(1-(xs**2))
      return(xs, ys, "-")
  </code></pre>
  
  <p>I am getting an error that states that an invalid value was encountered in a squareroot. I can't see what it is.</p>
  
  <pre><code>sqrt(0) = 0
  6.5*sqrt(1- (-1**2)) = 0
  </code></pre>
  
  <p>They should work, but the y values are having problems, they are returning "nan"</p>