1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.
  2. Hi Guest, welcome to the TES Community!

    Connect with like-minded education professionals and have your say on the issues that matter to you.

    Don't forget to look at the how to guide.

    Dismiss Notice

Uncertainty in 1/x

Discussion in 'Mathematics' started by Newstein, Jan 17, 2019.

  1. Newstein

    Newstein New commenter

    If x = (10.0 +- 0.1) cm, 1/x = (0.10 +- ?)
    I placed this qn in Science also.
     
  2. Newstein

    Newstein New commenter

    If y = 1/x,
    dy/dx = - 1/x^2
    mod delta y = (1/x^2) delta x
    And for x = 10.0, delta y = (1/100) times 0.1 = 0.001
    Sounds incorrect. Can uncertainty in 1/x be less than that of x?
     
  3. gnulinux

    gnulinux Occasional commenter

    Yes. You have more or less demonstrated that for x=10. What about for other values of x???
     
  4. briancant

    briancant Occasional commenter

    Well I've had a couple of beers but you work out the percentage uncertainty of 1 and 10 and add them. Given their is no uncertainty in 1 and the percentage uncertainty in 10 is 1% the uncertainty in 0.1 is 1% of 0.1. So = 0.1 +- 0.001.

    And if that make sense tomorrow I'll be amazed!!
     
  5. NoSuchThingAsNormal

    NoSuchThingAsNormal New commenter

    The error is the same in the reciprocal as it is in x, surely?

    x = 1 +/- 5%
    1/x ~ 1 +/- 5%
     
  6. briancant

    briancant Occasional commenter

    How does an absolute uncertainty of +-0.1 from a measurement of 10.0 equate to 5%? Surely this is 1%?
     

Share This Page