Editing Bessel function (section)

=== Astronomical problems ===
In 1770, Lagrangre introduced the series expansion of Bessel functions to solve [[Kepler's equation]], a trascendental equation in astronomy. [[Friedrich Wilhelm Bessel]] had seen Lagrange's solution but found it difficult to handle. In 1813 in a letter to [[Carl Friedrich Gauss]], Bessel simplified the calculation using trigonometric functions.<ref name=":0" /> Bessel published his work in 1819, independently introducing the method of Fourier series unaware of the work of Fourier which was published later.<ref name=":0" />
In 1824, Bessel carried out a systematic investigation of the functions, which earned the functions his name.<ref name=":0" /> In older literature the functions were called cylindrical functions or even Bessel–Fourier functions.<ref name=":0" />