Integrating e^x /x using Laurent series

In summary, the conversation discusses different methods for integrating \int_{}^{} \frac{e^x}{x}dx, including using a Laurent series, integration by parts, and searching for the function in Abramowitz and Stegun's book. However, it is concluded that the function is not a good candidate for integration by parts.
  • #1
pivoxa15
2,255
1
How does one integrate [tex]\int_{}^{} \frac{e^x}{x}dx[/tex]

I could expand it using a Laurent series and than integrating term by term but are there more elementary methods?
 
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  • #2
courtrigrad said:
why can't you just use integration by parts twice? [tex] \int e^{x}\frac{1}{x} dx [/tex], [tex] u = e^{x}, du = e^{x}dx, dv = \frac{1}{x}, v = \ln x [/tex]
This just keeps expanding. Using ILATE, the algebraic part should be u, but this just keeping increasing in the power on the bottom. I don't think it's a good candidate for parts.

Edit: I'm not sure what happened to that post. Disregard I guess.
 
  • #3
Since

[tex]\int \frac{e^{x}}{x} \ dx =\mbox{Ei}\left(x)[/tex]

you can search Abramowitz & Stegun's book on series expansion for this function.

Daniel.
 

FAQ: Integrating e^x /x using Laurent series

What is the definition of a Laurent series?

A Laurent series is a representation of a complex function as an infinite sum of powers of the variable, including negative powers.

Why is it useful to use a Laurent series to integrate e^x/x?

A Laurent series allows us to express a complex function in a compact and easily manipulatable form, making it easier to perform integrations and other calculations.

How do you find the Laurent series for e^x/x?

The Laurent series for e^x/x can be found by using the Maclaurin series for e^x and then manipulating it to include negative powers of x.

What is the radius of convergence for the Laurent series of e^x/x?

The radius of convergence for the Laurent series of e^x/x is the distance from the center of the series to the nearest singularity, which in this case is x=0. So the radius of convergence is 0.

Can the Laurent series for e^x/x be used to calculate the integral of e^x/x for any value of x?

No, the Laurent series for e^x/x is only valid for values of x within its radius of convergence, which in this case is 0. For other values of x, alternative methods of integration must be used.

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