1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Numerical analisys close numbers question

  1. Mar 29, 2010 #1
    [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?
     
  2. jcsd
  3. Mar 29, 2010 #2

    Mark44

    Staff: Mentor

    If x is very close to 0, you're subtracting 1 from a number that is very close to 1.
     
  4. Mar 29, 2010 #3
    thanks :)
     
  5. Mar 29, 2010 #4
    why multiplying and dividing by [tex]y=\sqrt{x^2+1}+1[/tex]
     
  6. Mar 29, 2010 #5

    Mark44

    Staff: Mentor

    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]
     
  7. Mar 29, 2010 #6
    we get x^2 in the nominator
    and a sum in the denominator
    now there is some stuff about relative error
    but i dont know what?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Numerical analisys close numbers question
Loading...