In mathematics, Rodrigues' formula (formerly called the Ivory–Jacobi formula) generates the Legendre polynomials. It was independently introduced by Olinde Rodrigues (1816), Sir James Ivory (1824) and Carl Gustav Jacobi (1827). The name "Rodrigues formula" was introduced by Heine in 1878, after Hermite pointed out in 1865 that Rodrigues was the first to discover it. The term is also used to describe similar formulas for other orthogonal polynomials. Askey (2005) describes the history of the Rodrigues formula in detail.

Statement

edit

Let   be a sequence of orthogonal polynomials defined on the interval   satisfying the orthogonality condition   where   is a suitable weight function,   is a constant depending on  , and   is the Kronecker delta. If the weight function   satisfies the following differential equation (called Pearson's differential equation),   where   is a polynomial with degree at most 1 and   is a polynomial with degree at most 2 and, further, the limits   Then it can be shown that   satisfies a relation of the form,   for some constants  . This relation is called Rodrigues' type formula, or just Rodrigues' formula.[1]

The most known applications of Rodrigues' type formulas are the formulas for Legendre, Laguerre and Hermite polynomials:

Rodrigues stated his formula for Legendre polynomials  :  

Laguerre polynomials are usually denoted L0L1, ..., and the Rodrigues formula can be written as  

The Rodrigues formula for the Hermite polynomials can be written as  

Similar formulae hold for many other sequences of orthogonal functions arising from Sturm–Liouville equations, and these are also called the Rodrigues formula (or Rodrigues' type formula) for that case, especially when the resulting sequence is polynomial.

References

edit
  1. ^ "Rodrigues formula – Encyclopedia of Mathematics". www.encyclopediaofmath.org. Retrieved 2018-04-18.