Relative uncertainty (negative exponent)

[KevinFan]

Homework Statement

A distance R is measured to be 3.400±0.003m. What is the relative uncertainty in R? 9×10-4
What is the relative uncertainty in R^-2?

Homework Equations

The Attempt at a Solution

Relative uncertainty of R is 0.003/3.4=8.8e-4
Relative uncertainty of R^-2= -2(8.8e-4)=-1.76e-3?
How do you calculate relative uncertainty with a negative exponent?

 

[mfb]

The relative uncertainy is always positive. The negative sign in your calculation indicates that a larger R leads to a smaller R^-2, but that is not relevant here, so you have to take the magnitude.

 

[KevinFan]

The relative uncertainy is always positive. The negative sign in your calculation indicates that a larger R leads to a smaller R^-2, but that is not relevant here, so you have to take the magnitude.

Thank you!