>>> """
========
Mathtext
========

Use Matplotlib's internal LaTeX parser and layout engine.  For true LaTeX
rendering, see the text.usetex option.
"""
... 
... import matplotlib.pyplot as plt
... 
... fig, ax = plt.subplots()
... 
... ax.plot([1, 2, 3], label=r'$\sqrt{x^2}$')
... ax.legend()
... 
... ax.set_xlabel(r'$\Delta_i^j$', fontsize=20)
... ax.set_ylabel(r'$\Delta_{i+1}^j$', fontsize=20)
... ax.set_title(r'$\Delta_i^j \hspace{0.4} \mathrm{versus} \hspace{0.4} '
...              r'\Delta_{i+1}^j$', fontsize=20)
... 
... tex = r'$\mathcal{R}\prod_{i=\alpha_{i+1}}^\infty a_i\sin(2 \pi f x_i)$'
... ax.text(1, 1.6, tex, fontsize=20, va='bottom')
... 
... fig.tight_layout()
... plt.show()
...