Numerical Integration: Simpson's Rule for 1/x

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Discussion Overview

The discussion revolves around the numerical integration of the function 1/x from 0 to 2 using Simpson's rule. Participants explore the implications of the function being undefined at x = 0 and the nature of the integral, including whether it exists as a proper or improper integral.

Discussion Character

  • Debate/contested
  • Mathematical reasoning
  • Exploratory

Main Points Raised

  • One participant questions how to apply Simpson's rule to the integral of 1/x from 0 to 2 due to the undefined nature of the function at x = 0.
  • Another participant asserts that the integral does not exist, suggesting a need to check the question.
  • A different participant confidently states that the antiderivative of 1/x is ln(x), but does not provide a proof, citing a lack of time.
  • Concerns are raised about the value of ln(x) as x approaches 0, indicating that the integral diverges as the endpoint approaches this limit.
  • One participant clarifies that the integral can be treated as an improper Riemann integral by taking limits, concluding that the result diverges to infinity.

Areas of Agreement / Disagreement

Participants express disagreement regarding the existence of the integral and the implications of using Simpson's rule. Some assert that the integral diverges, while others maintain that it can be evaluated under certain conditions.

Contextual Notes

The discussion highlights the complexities of evaluating improper integrals and the assumptions involved in numerical integration methods. There are unresolved mathematical steps related to the limits and the behavior of the function near x = 0.

irony of truth
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I am performing the numerical integration of finding the area of 1/x dx from 0 to 2... using Simpson's rule of n = 6. What will I do in this problem like this since 0 to be evaluated in the f(x) = 1/x is undefined?
 
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I'd check the question since the integral doesn't exist.
 
I'm sure it does.

The integral(anti-derivative) is ln x.

I'm pretty darn confident that's what it is. I'd prove it, but I'm not in the mood to spend time on here, and last time I tried Latex it didn't work.

y = ln x

dy/dx = 1/x
 
if you are so concerned about your time why are you wasting ours?
 
JasonRox said:
I'm sure it does.

The integral(anti-derivative) is ln x.

I'm pretty darn confident that's what it is. I'd prove it, but I'm not in the mood to spend time on here, and last time I tried Latex it didn't work.

y = ln x

dy/dx = 1/x

Yes, but what is the value of ln(x) when x = 0? Even if you try to avoid that limit of integration your answer will diverge as you move your endpoint closer to x = 0.
 
the integral, as an improper riemann integral (limit h to zero of int from h to 2) does not exist, Jason. The function has an antiderivative, and that can be used to prove this fact.
 
mathwonk said:
if you are so concerned about your time why are you wasting ours?

Relative to me, your time is going slow, so you might as well take advantage of it. :biggrin:

Kidding.

Sorry, I was getting ready to go to bed, and Latex in fact didn't work last time.

Should of checked my answer, and yes it is wrong.
 
irony of truth said:
I am performing the numerical integration of finding the area of 1/x dx from 0 to 2... using Simpson's rule of n = 6. What will I do in this problem like this since 0 to be evaluated in the f(x) = 1/x is undefined?

You can still use Simpson method,though the integral is improper,by taking the limits of the integral as being from 'a' to 2 (where 'a' tends to 0).Finally take the limit for a->0 from the expression in 'a' obtained after applying Simpson's method.The results is ∞,the integral diverges.
 

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