Legendre polynomial - recurrence relations

In summary, the conversation discusses using induction to prove the legendre polynomial $P_{n+1}(x) = (2n+1)P_n(x) + P'_{n-1}(x)$ and the suggested approach is to prove it for n=1 and then show that if it's true for n=m, it implies it's true for n=m+1. The person is asked to try and provide their work up to the point where they get stuck.
  • #1
Joe20
53
1
Homework Statement
As attached
Relevant Equations
As attached
Note: $P_n (x)$ is legendre polynomial

$$P_{n+1}(x) = (2n+1)P_n(x) + P'_{n-1}(x) $$
$$\implies P_{n+1}(x) = (2n+1)P_n(x) + \sum_{k=0}^{\lfloor\frac{n}{2}\rfloor} (2(n-1-2k)+1)P_{n-1-2k}(x))$$

How can I continue to use induction to prove this? Help appreciated.
 

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  • #2
To prove something by induction, you need to do two things:
Prove it's true for n=1.

Prove that if it's true for n=m, that implies it's true for n=m+1.

The first part at least is usually pretty easy. Why don't you try to get as far as you can and post your work where you get stuck?
 
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Likes vanhees71 and Greg Bernhardt

1. What are Legendre polynomials and what are they used for?

Legendre polynomials are a set of orthogonal polynomials that are commonly used in mathematical analysis, particularly in the field of physics. They are named after French mathematician Adrien-Marie Legendre and are used to solve differential equations, perform numerical integration, and represent functions in a series.

2. What is the recurrence relation for Legendre polynomials?

The recurrence relation for Legendre polynomials is Pn+1(x) = (2n+1)xPn(x) - nPn-1(x), where Pn(x) represents the Legendre polynomial of degree n. This relation allows for the calculation of higher degree polynomials using lower degree ones.

3. How are Legendre polynomials related to spherical harmonics?

Legendre polynomials are closely related to spherical harmonics, which are functions used to represent solutions to Laplace's equation in spherical coordinates. The spherical harmonics are a product of the Legendre polynomials and a trigonometric function, and they are used to describe the behavior of waves and fields in spherical systems.

4. What is the significance of the recurrence relation in Legendre polynomials?

The recurrence relation in Legendre polynomials is significant because it allows for the efficient calculation of higher degree polynomials using lower degree ones. This makes it easier to work with Legendre polynomials and use them in various mathematical applications.

5. Are there any other recurrence relations for Legendre polynomials?

Yes, there are several other recurrence relations for Legendre polynomials, including the Rodrigues' formula and the generating function. These relations can be used to derive the recurrence relation mentioned earlier and provide alternative methods for calculating Legendre polynomials.

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