We will end this chapter with some special mathematical functions. Bessel functions are solutions of the Bessel differential equations (visit http://en.wikipedia.org/wiki/Bessel_function). The modified Bessel function of the first kind 0th order is represented in NumPy by i0. The sinc function is represented in NumPy by a function with the same name and there is also a two-dimensional version of this function. sinc is a trigonometric function; for more details visit http://en.wikipedia.org/wiki/Sinc_function.