Finding relative error for radial acceleration

[ooohffff]

Homework Statement

I'm trying to find da/a to calculate the relative possible error in the radial acceleration. The equation I have to derive from is a = 4π²n²rt ⁻² (it cannot be a = v²/r). I'm not really sure how to find da since it has 3 variables?

Homework Equations

a = 4π²n²rt ⁻²
da/a = ?

The Attempt at a Solution

I'm assuming you use the u-substitution method...? Any tips or websites that can help me do this?

 

[cnh1995]

a = 4π²n²rt ⁻²

Take natural log on both sides and then differentiate w.r.t a. You'll need the chain rule of differentiation.