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Homework Help: Uncertainty/error question

  1. Oct 1, 2008 #1
    1. The problem statement, all variables and given/known data

    If the relative error of m is 1% and of h is .5%, what is the error of log(mh)?

    2. Relevant equations

    d/dx(lnx)=1/x, [tex]\delta[/tex]lnx=[tex]\delta[/tex]x/x

    3. The attempt at a solution
    [tex]\delta[/tex](ln0.43(mh))=[tex]\delta[/tex](0.43lnm + 0.43lnh)
    =[tex]\delta[/tex](0.43ln0.01 + 0.43ln0.005)

    i'm pretty sure this isn't right since it's a negative number, i have no idea how to do this
  2. jcsd
  3. Oct 2, 2008 #2


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    Staff Emeritus
    Science Advisor
    Homework Helper

    I don't see how the 0.43 is coming into this.

    First, what's the relative error in m*h?

    Second, if you want the error in ln(x), replace x with x0(1±ε). (ε is the relative error in x).

    See if you can work it from there.
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