# Homework Help: Uncertainty/error question

1. Oct 1, 2008

### excel000

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, $$\delta$$lnx=$$\delta$$x/x

3. The attempt at a solution
$$\delta$$(ln0.43(mh))=$$\delta$$(0.43lnm + 0.43lnh)
=$$\delta$$(0.43ln0.01 + 0.43ln0.005)
=-4.26

i'm pretty sure this isn't right since it's a negative number, i have no idea how to do this

2. Oct 2, 2008

### Redbelly98

Staff Emeritus
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.