Legendre Second Kind: $Q_n(x)$ Functions

In summary, the conversation discusses the Legendre functions $Q_n(x)$ of the second kind and how to reach the formula $Q_n(x)=\frac{1}{2} P_n(x)\ln\left( \frac{ 1+x}{1-x}\right)$ from the equation $Q_n(x)=P_n(x) \int \frac{1}{(1-x^2)\cdot P_n^2(x)}\, \mathrm{d}x$. The question arises about whether the two forms for $Q_n(x)$ are equal and it is suggested to check the formulas.
  • #1
jije1112
10
0
Legendre functions $Q_n(x)$ of the second kind
\begin{equation*}
Q_n(x)=P_n(x) \int \frac{1}{(1-x^2)\cdot P_n^2(x)}\, \mathrm{d}x
\end{equation*}
what to do after this step?
how can I complete ?
I need to reach this formula
\begin{equation*}
Q_n(x)=\frac{1}{2} P_n(x)\ln\left( \frac{ 1+x}{1-x}\right)
\end{equation*}
 
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  • #2
If that were true then, setting the two forms for [itex]Q_(x)[/itex] equal, it would have to be true that
[tex]\int \frac{1}{(1- x^2)P^2_n(x)}dx= \frac{1}{2}ln\left(\frac{1+ x}{1- x}\right)[/tex]

Is that true? I suggest you check your formulas.
 

What is the Legendre Second Kind: $Q_n(x)$ function?

The Legendre Second Kind function, also known as the Ferrers function, is a special type of mathematical function used in the study of spherical harmonics and other areas of physics and mathematics. It is defined as the solution to a specific differential equation and is closely related to the more well-known Legendre First Kind function.

What is the purpose of the Legendre Second Kind: $Q_n(x)$ function?

The Legendre Second Kind function has several important uses in physics and mathematics. It is commonly used in the study of spherical harmonics, which are essential in the analysis of electromagnetic fields and quantum mechanics. It also plays a crucial role in solving boundary value problems and differential equations in mathematical physics.

How is the Legendre Second Kind: $Q_n(x)$ function related to the Legendre First Kind function?

The Legendre Second Kind function is closely related to the Legendre First Kind function. In fact, they are both solutions to the same differential equation, but with different boundary conditions. The Legendre Second Kind function is defined for values of x greater than 1, while the Legendre First Kind function is defined for values of x between -1 and 1.

What are the properties of the Legendre Second Kind: $Q_n(x)$ function?

Some of the key properties of the Legendre Second Kind function include orthogonality, recursion, and symmetry. These properties make it a powerful tool for solving complex mathematical problems in physics and engineering. Additionally, the function is infinitely differentiable and has a unique set of zeros and poles.

How is the Legendre Second Kind: $Q_n(x)$ function used in real-world applications?

The Legendre Second Kind function has numerous real-world applications, particularly in physics and engineering. It is used in the analysis of electromagnetic fields, quantum mechanics, and heat transfer problems. It is also utilized in solving boundary value problems in mathematical physics and in the design of antennas and other electronic devices.

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