title: LaTeX not working on matplotlib text
body: <p>I've been having this trouble for a long time whenever I want to render LaTeX for plot labelling and text, it works sometimes for some symbols but not others. For example in my script shown here generates the plot below: </p>
  
  <pre><code>from matplotlib import rc
  plt.rc('text', usetex=True)
  plt.plot(a_t,asol[:,0],label ='$\psi$')
  plt.plot(a_t,rho,label ="$\rho/\rho_c$")
  plt.xlabel(r"$\xi$",fontsize=15)
  from matplotlib.legend_handler import HandlerLine2D
  plt.legend(loc='upper left',prop={'size':12},numpoints=1)
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/i7pK4.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/i7pK4.png" alt="plt_result"></a></p>
  
  <p>I've tried other symbols, $\pi$ works okay but $\theta$ only shows "heta" without the t. I'm confused by why some symbols works for LaTeX and some don't.</p>
  
  <p>Thanks!</p>