IPython notebook uses MathJax to render LaTeX inside html/markdown. Just put your LaTeX math inside $$.
$$c = \sqrt{a^2 + b^2}$$

You have to write :
import matplotlib.pyplot as plt
import numpy as np
x = np.linspace(0,3)
y = np.sin(x)
plt.plot(x,y)
plt.title(r'$$\beta \rho \lambda \xi$$',fontsize=30)
plt.show()
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Or you can display LaTeX / Math output from Python, as seen towards the end of the notebook tour :
from IPython.display import display, Math, Latex
display(Math(r'F(k) = \int_{-\infty}^{\infty} f(x) e^{2\pi i k} dx'))

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Other kind of solution :
import numpy as np
from matplotlib import pyplot as plt
import matplotlib as mpl
mpl.rcParams['text.usetex'] = True
mpl.rcParams['text.latex.preamble'] = [r'\usepackage{amsmath}'] #for \text command
x = np.linspace(0,3)
y = np.sin(x)
plt.plot(x,y)
plt.title(r'$text{\beta \rho \lambda \xi}$',fontsize=30)
plt.show()