title: Plotting cosine with Python
body: <p>I plot a cosine sampled at 400 points in the interval -5 .. +5 using python for n=1..4:</p>
  
  <pre><code>import matplotlib.pyplot as plt
  import numpy
  
  for n in range(1,5):
      x = numpy.linspace(-5,5,num=400)
      series = numpy.cos(1e4/n*x)
      plt.figure()
      plt.plot(series)
  </code></pre>
  
  <p>But for n = 3 the plot looks not like a cosine which I think is due to sampling error. How can I achieve a smooth cosine plot with constant samples for different frequencies (i.e. different n)?</p>