Legendre Polynomial and Rodrigues' Formula

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SUMMARY

The discussion focuses on the derivation of the integral of Legendre polynomials using Rodrigues' formula, specifically for odd and even terms. The integral for odd terms is given by the equation \int_0^1dx\;P_l(x)=\left(-\frac{1}{2}\right)^{\frac{l-1}{2}}\frac{(l-2)!}{2\left(\frac{l+1}{2}\right)!}. The proof for odd terms can be found in "Special Functions for Scientists and Engineers" by W.W. Bell, while the even terms yield an integral result of zero for all higher even l. The generating function provides a more straightforward method for deriving these results.

PREREQUISITES
  • Understanding of Legendre polynomials
  • Familiarity with Rodrigues' formula
  • Knowledge of integral calculus
  • Experience with generating functions in mathematical analysis
NEXT STEPS
  • Study the derivation of Legendre polynomials using Rodrigues' formula
  • Explore the generating function for Legendre polynomials
  • Review "Special Functions for Scientists and Engineers" by W.W. Bell for detailed proofs
  • Investigate the properties of integrals involving orthogonal polynomials
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This discussion is beneficial for physicists, mathematicians, and students studying electrodynamics or advanced calculus, particularly those interested in special functions and their applications in physics.

kiwakwok
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I am reading Jackson's electrodynamics book. When I went through the Legendre polynomial, I have a question.

In the book, it stated that from the Rodrigues' formula we have
Consider only the odd terms
\int_0^1dx\;P_l(x)=\left(-\frac{1}{2}\right)^{\frac{l-1}{2}}\frac{(l-2)!}{2\left(\frac{l+1}{2}\right)!}​
How to obtain this equation and how can I obtain the equation for even terms?

Thanks in advance.
 
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The general formula (irrespective of l even or odd) is

http://www.wolframalpha.com/input/?i=Evaluate+integral+from+0+to+1+LegendreP[n,z]+dz

or set \sigma=0 in the formula (807) 7.126.1 in Gradshteyn-Ryzhik.

The whole proof for l=odd is in Bell, W.W."Special Functions for Scientists and Engineers", (VanNostrand, 1967) as Example 2 on Page 86.

You can make the proof by yourself with help of the fully solved case l=odd by making the necessary changes in the proof already given.
 
The formula is more easily derived using the generating function.
The integral equals 1 for l=0, and is zero for all higher even l.
 

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