Need help with Rodrigues formula example in Riley, Hobson, Bence - Mathematical Methods for Physics and Engineering 3rd edition

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Discussion Overview

The discussion revolves around understanding the steps involved in deriving the Rodrigues formula as presented in the textbook "Mathematical Methods for Physics and Engineering" by Riley, Hobson, and Bence. Participants seek clarification on specific formulas and terms related to the recurrence relation and its implications in the context of the formula.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant requests clarification on the steps between two specific formulas on page 582 of the textbook.
  • Another participant presents a recurrence relation for K_l and explains how it can be derived by substituting previous terms until reaching K_0.
  • A different participant questions the origin of a specific term, ## 2^l l! ##, in the formula, noting its presence in the numerator.
  • One participant suggests that the expression might relate to double factorials but does not provide a definitive explanation.
  • A subsequent request for further clarification indicates that not all participants are satisfied with the explanations provided.

Areas of Agreement / Disagreement

There is no consensus on the derivation of the specific term in question, and multiple viewpoints are presented regarding the recurrence relation and its implications. The discussion remains unresolved as participants seek further clarification.

Contextual Notes

Some assumptions regarding the recurrence relation and the definitions of terms like double factorial may not be fully articulated, leading to potential gaps in understanding.

vgarg
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Can someone please show/explain to me the steps between the 2 circled formulas on the attached page #582 from Riley, Hobson, Bence - Mathematical Methods for Physics and Engineering 3rd edition.

Thank you!
 

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We can write the recurrence relation as K_l = \frac{2l}{2l+1} K_{l-1}.
We get the formula on the left-hand side when we substitute K_{l-1} with K_{l-1} = \frac{2l-1}{2(l-1)+1} K_{l-1-1}.
We can repeat this process until we get to l = 1 and K_0 (because of the assumption just below the grey box).
The part most on the right of the circle below is a compact way to write this product.
 
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Thank you!
Could you please explain where does the 2nd ## 2^l l! ## term in ## 2^l l! \frac{2^l l!}{(2l+1)!} 2 ## in the lower circle come from? It has two ## 2^l l! ## terms in the numerator.
 
Thank you!
Can someone else please try to explain this to me?
 

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