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How should I calculate uncertainties?

  1. Sep 11, 2010 #1
    1. The problem statement, all variables and given/known data

    I'm writing up a prac, which involves calculating the uncertainty for 1/(xy)^0.5.

    There are two formulas that I think apply:

    2. Relevant equations

    For R = xy, u(R)/R = u(x)/x + u(y)/y


    using differentials in calculus

    dR = (dR/dx)dx + (dR/dy)dy [note that dR/dr and dR/dy are partials]

    3. The attempt at a solution

    I found the latter formula in a calculus textbook. It does not appear in the lab manual. However, I'm thrown by the fact that R depends on the square root of xy. I'm not sure if the first formula applies in this case.

    Does anyone know the right approach?

  2. jcsd
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