Bessel function definitions

Bessel function

for an arbitrary complex number α (the order of the Bessel function). The most important cases are for α an integer or half-integer. Although α and −α produce the same differential equation for real α, it is conventional to define different Bessel functions for these two values in such a way that the Bessel functions are mostly smooth funct...
Found on http://en.wikipedia.org/wiki/Bessel_function

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Bessel function

any of a set of mathematical functions systematically derived around 1817 by the German astronomer Friedrich Wilhelm Bessel during an investigation ... [2 related articles]
Found on http://www.britannica.com/eb/a-z/b/55

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Bessel function

one of several transcendental functions, usually represented as power series, that are solutions to a group of related differential equations.
Found on https://www.infoplease.com/dictionary/bessel-function

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