Why do some integrals require correction for extreme precision?

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Discussion Overview

The discussion revolves around the need for corrections in integrals, particularly simple ones like y=x², when aiming for extreme precision. Participants explore the implications of numerical versus analytical integration and the potential errors involved in different methods.

Discussion Character

  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions whether simple integrals require corrections for extreme precision and seeks clarification and resources.
  • Another participant asserts that analytically solvable integrals, such as the integral of x², do not need corrections, suggesting that precision is inherently perfect in such cases.
  • A different viewpoint emphasizes that numerical integration methods introduce errors due to the limitations of computational precision, implying that corrections may be necessary in practical applications.
  • Participants discuss various numerical methods for integration, including the trapezoid rule and Simpson's rule, indicating that these methods can yield imprecise results compared to analytical solutions.
  • There is a correction regarding the formula for the integral of x², with one participant initially misstating it, leading to a clarification of the correct expression.

Areas of Agreement / Disagreement

Participants express differing views on whether corrections are needed for simple integrals. Some argue that analytical solutions are exact, while others highlight the imprecision of numerical methods, indicating an unresolved debate on the topic.

Contextual Notes

Limitations in the discussion include the lack of a clear definition of "extreme precision" and the dependence on the context in which integrals are applied, particularly regarding numerical methods.

bobie
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I have read that even the simplest integrals (like y=x2) might need some correction if we want to reach an extreme precision. Is that really so?
Can you explain why or give me some useful links?
Thanks
 
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bobie said:
I have read that even the simplest integrals (like y=x2) might need some correction if we want to reach an extreme precision. Is that really so?
Can you explain why or give me some useful links?
Thanks

Define "extreme precision".

Integrals which can be done analytically (such as the integral of [itex]x^2[/itex]) cannot be more precise.

If you can only do an integral numerically then you are constrained by the fact that computers can only ever do a finite number of calculations on a finite subset of the rational numbers, so there's always going to be some error; the question is whether the error can be made small enough so that you can ignore it in the context of whatever your actual problem is.
 
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bobie said:
I have read that even the simplest integrals (like y=x2) might need some correction if we want to reach an extreme precision. Is that really so?
Can you explain why or give me some useful links?
Thanks

No. ## \int_a^b x^2 \,dx = 2(b - a) ## there is no "correction" involved.

Can you explain why you think this or give us a useful link?
 
MrAnchovy said:
No. ## \int_a^b x^2 \,dx = 2(b - a) ## there is no "correction" involved.

Don't you mean,

[tex]\int_a^bx^2 dx = \frac{1}{3}\left( b^3 - a^3 \right)?[/tex]
 
bobie said:
I have read that even the simplest integrals (like y=x2) might need some correction if we want to reach an extreme precision. Is that really so?
If you use a numerical technique, the results are generally imprecise. As already mentioned in this thread, if you are lucky enough to know the antiderivative of the function you're integrating, the results will be exact.
bobie said:
Can you explain why or give me some useful links?
Thanks
There are lots of numerical methods for integration - trapezoid rule, Simpson's rule, many others. See http://en.wikipedia.org/wiki/Numerical_integration for more information.
 
collinsmark said:
Don't you mean,
[tex]\int_a^bx^2 dx = \frac{1}{3}\left( b^3 - a^3 \right)?[/tex]
Oops yes of course, thank you - now how did that happen? :blush:
 

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