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Writing Uncertainty in terms of dA, dB, dC

  • 01-10-2012 5:44pm
    #1
    Smythe
    Registered Users, Registered Users 2 Posts: 434 ✭✭


    A question states:

    Write down formulae for dX in terms of dA, dB, dC if:
    X = [(A) (B^2)] / C

    I'm using the formula below as this corresponds to this relationship.
    (dX/X)^2 = (dA/A)^2 + (dB/B)^2


    For the first line, not the actual solution, I'm getting either:

    (dX/X)^2 = (dA/A)^2 + (2dB/B)^2 + (dC/C)^2
    or
    (dX/X)^2 = (dA/A)^2 + (dB/B)^2 + (dB/B)^2 + (dC/C)^2

    Then if I follow through on either line, I get a different answer.

    I was wondering which is the correct line to begin with?

    I think it's the second option.

    Thank you.


Comments

  • #2
    mcdbd
    Registered Users, Registered Users 2 Posts: 39 ✭mcdbd


    Line 1 is correct. I have An Introduction to Error Analysis by J. Taylor. Its a great book for clearing these things up.


  • #3
    Smythe
    Registered Users, Registered Users 2 Posts: 434 ✭✭Smythe


    I was so sure it was the 2nd line...

    I'll check out that book.

    Thanks mcdbd


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