title: How to draw an unit circle using numpy and matplotlib
body: <p>I want to draw an unit circle(cos+sin), using numpy and matplotlib.
  I wrote the following:</p>
  
  <pre><code>t = np.linspace(0,np.pi*2,100)
  circ = np.concatenate((np.cos(t),np.sin(t)))
  </code></pre>
  
  <p>and I plotted, but failed.</p>
  
  <pre><code>ax.plot(t,circ,linewidth=1)
  ValueError: x and y must have same first dimension
  </code></pre>