Finding a power series expansion for a definite integral

In summary, the conversation discusses finding a power series expansion for the function f(x) = ^{1}_{0}\int\frac{1 - e^{-sx}}{s} ds, using the power series expansion formula. The individual has attempted various methods but encountered difficulties. Eventually, they realize that substituting the Taylor series for e^{-sx} in the integrand and integrating will solve the problem.
  • #1
Szichedelic
29
0

Homework Statement



Find a power series expansion about x = 0 for the function

f(x) = [itex]^{1}_{0}\int\frac{1 - e^{-sx}}{s}[/itex] ds


Homework Equations



The power series expansion for a function comes of the form f(x) = [itex]^{\infty}_{0}\sum a_{k}x^{k}[/itex]


The Attempt at a Solution



I've tried several things to start off with but quickly end up hitting a dead end road. First, I tried just simply taking the integral, but quickly found it isn't defined at 0 (hence why they are asking me to find a power series expansion for it). Then, I tried finding a power series expansion for the innerpart of the integral and ran into the same problem.
 
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  • #2
Szichedelic said:

Homework Statement



Find a power series expansion about x = 0 for the function

f(x) = [itex]^{1}_{0}\int\frac{1 - e^{-sx}}{s}[/itex] ds

Homework Equations



The power series expansion for a function comes of the form f(x) = [itex]^{\infty}_{0}\sum a_{k}x^{k}[/itex]

The Attempt at a Solution



I've tried several things to start off with but quickly end up hitting a dead end road. First, I tried just simply taking the integral, but quickly found it isn't defined at 0 (hence why they are asking me to find a power series expansion for it). Then, I tried finding a power series expansion for the innerpart of the integral and ran into the same problem.

Did you try substituting the Taylor series (as a function of x) for ##e^{-sx}## in the integrand, simplifying and integrating?
 
  • #3
Yeah, I figured that out shortly after I posted this. Can't believe I overlooked that! Thanks!
 

What is a power series expansion for a definite integral?

A power series expansion for a definite integral is a representation of a function as an infinite sum of terms, each of which is a constant multiplied by a variable raised to a non-negative integer power, that is used to approximate a definite integral. This expansion allows us to evaluate the integral with a high degree of accuracy by using a finite number of terms.

Why is finding a power series expansion for a definite integral useful?

Finding a power series expansion for a definite integral can be useful in situations where the integral cannot be evaluated using traditional methods, such as integration by substitution or by parts. It allows us to approximate the integral and find an accurate solution without having to use complex techniques.

How do you find a power series expansion for a definite integral?

To find a power series expansion for a definite integral, we first need to identify the function that we want to integrate. Then, we use the formula for a power series expansion to write the function as an infinite sum of terms. Finally, we integrate each term of the series to obtain the power series expansion for the definite integral.

What are the limitations of using a power series expansion for a definite integral?

One limitation of using a power series expansion for a definite integral is that it only works for certain types of functions. In some cases, the series may not converge or may converge very slowly, making it difficult to obtain an accurate solution. Additionally, the accuracy of the approximation depends on the number of terms used in the series, so it may not always provide a precise answer.

Can a power series expansion for a definite integral be used to find exact solutions?

No, a power series expansion for a definite integral can only provide an approximation of the solution. It cannot be used to obtain an exact answer, but it can give us a very accurate estimation of the value of the integral.

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