Numerical analisys close numbers question

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Homework Help Overview

The discussion revolves around the concept of loss of significance in numerical analysis, particularly in the context of the expression y = √(x² + 1) - 1. Participants explore the implications of subtracting two close numbers and the effects of manipulating the expression through multiplication and division.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants question the presence of close numbers in the expression and the conditions under which loss of significance occurs. There is a discussion about the effect of multiplying and dividing by y = √(x² + 1) + 1 to eliminate this issue. Some participants provide specific scenarios, such as when x is close to 0, to illustrate their points.

Discussion Status

The discussion is ongoing, with participants sharing insights and questions about the mathematical manipulation of the expression. Some have provided partial explanations regarding the multiplication and division process, while others express uncertainty about concepts like relative error.

Contextual Notes

There appears to be a focus on understanding the implications of numerical stability and error in calculations involving small differences. Participants are navigating through assumptions related to the behavior of the expression as x approaches certain values.

nhrock3
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[tex]y=\sqrt{x^2+1}-1[/tex]
how do we know that there is a subtraction of two close numbers thus making loss of significance?
there is no close numbers there is variable X
it could give use a close result or otherwise

and why multiplying and dividing by [tex]y=\sqrt{x^2+1}+1[/tex]
makes it go away?
 
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nhrock3 said:
[tex]y=\sqrt{x^2+1}-1[/tex]
how do we know that there is a subtraction of two close numbers thus making loss of significance?
there is no close numbers there is variable X
it could give use a close result or otherwise

and why multiplying and dividing by [tex]y=\sqrt{x^2+1}+1[/tex]
makes it go away?

If x is very close to 0, you're subtracting 1 from a number that is very close to 1.
 
thanks :)
 
why multiplying and dividing by [tex]y=\sqrt{x^2+1}+1[/tex]
 
What do you get when you do this multiplication?
[tex]\left(\sqrt{x^2+1}-1\right)\frac{\sqrt{x^2+1}+1}{\sqrt{x^2+1}+1}[/tex]
 
we get x^2 in the nominator
and a sum in the denominator
now there is some stuff about relative error
but i don't know what?
 

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