Integrating $\frac{1}{x^r-1}$ with r>1

  • MHB
  • Thread starter bincy
  • Start date
  • Tags
    Integrating
In summary, the conversation discusses the integral $\int \frac{1}{x^r-1}dx$ where $r$ is a real number greater than $1$. The first part of the conversation suggests that this integral may not be expressible in terms of elementary functions. However, it is possible to integrate the expression term by term. If $|x|<1$, the integral can be expressed as $- \sum_{n=0}^{\infty} x^{n\ r}$. On the other hand, if $|x|>1$, the integral can be rewritten as $- \sum_{n=0}^{\infty} t^{(n+1)\ r-2}$
  • #1
bincy
38
0
Hii Everyone,\(\displaystyle \int\frac{1}{x^{r}-1}dx
\) where r is a real no. greater than 1regards,
Bincy
 
Physics news on Phys.org
  • #2
bincybn said:
Hii Everyone,\(\displaystyle \int\frac{1}{x^{r}-1}dx
\) where r is a real no. greater than 1regards,
Bincy

Hi Bincy, :)

This integral may not be expressible in terms of elementary functions. See this.

Kind Regards,
Sudharaka.
 
  • #3
If $|x|<1$ then is...

$\displaystyle \frac{1}{x^{r}-1} = - \sum_{n=0}^{\infty} x^{n\ r}$ (1)

... and You can integrate the expression (1) 'term by term'...

Kind regards

$\chi$ $\sigma$
 
  • #4
chisigma said:
If $|x|<1$ then is...

$\displaystyle \frac{1}{x^{r}-1} = - \sum_{n=0}^{\infty} x^{n\ r}$ (1)

... and You can integrate the expression (1) 'term by term'...

... and if $|x|>1$ then You can set $\displaystyle t=\frac{1}{x}$ and the function to be integrated becomes...

$\displaystyle \frac{1}{t^{2}\ \{1-(\frac{1}{t})^{r}\}}\ = - \sum_{n=0}^{\infty} t^{(n+1)\ r-2}$ (1)

... and also in this case You can integrate 'term by term'...

Kind regards

$\chi$ $\sigma$
 
  • #5
Can you please explain me the source of these formula?
 
  • #6
bincybn said:
Can you please explain me the source of these formula?

chisigma is just using the sum of an infinite geometric series:

\[\sum_{n=0}^{\infty} x^n = \frac{1}{1-x}, \ \ \text{for } |x|<1\]

which should be common knowledge.

CB
 

FAQ: Integrating $\frac{1}{x^r-1}$ with r>1

What does it mean to integrate $\frac{1}{x^r-1}$ with r>1?

Integrating $\frac{1}{x^r-1}$ with r>1 means finding the indefinite integral of the function $\frac{1}{x^r-1}$, where r is greater than 1. This involves finding a function whose derivative is equal to $\frac{1}{x^r-1}$.

What is the significance of r>1 in the integration of $\frac{1}{x^r-1}$?

The value of r determines the type of integral that must be used to integrate $\frac{1}{x^r-1}$. When r is greater than 1, the integral will be a logarithmic or inverse tangent integral.

Can $\frac{1}{x^r-1}$ be integrated using basic integration techniques?

No, $\frac{1}{x^r-1}$ cannot be integrated using basic integration techniques such as the power rule or substitution. It requires more advanced techniques such as partial fractions or trigonometric substitutions.

What are the applications of integrating $\frac{1}{x^r-1}$ with r>1?

Integrating $\frac{1}{x^r-1}$ with r>1 has applications in various fields such as physics, engineering, and economics. It can be used to solve problems involving exponential growth and decay, as well as in the analysis of electrical circuits and financial markets.

Are there any limitations to integrating $\frac{1}{x^r-1}$ with r>1?

Yes, there are limitations to integrating $\frac{1}{x^r-1}$ with r>1. In some cases, the integral may not have a closed form solution and must be evaluated numerically. Additionally, the integral may not exist for certain values of r, such as when r is equal to 1 or a negative integer.

Similar threads

Back
Top