# Rearranging and Exponentials

1. Jan 19, 2012

### annalise17

1. The problem statement, all variables and given/known data
I believe I need to rearrange this formula to find an equation for λ:

P2 / P1 = exp( - (z2 - z1)) / λ

2. Relevant equations
I think I need to differentiate and find the natural log of both sides then rearrange

3. The attempt at a solution
Differentiate to: ln(P2 / P1) = ( - (z2 - z1) / λ

Rearrange to: λ = - Δz / ln(P2 / P1)

Does that look right? I appear to be able to calculate it....

2. Jan 19, 2012

Is this what you're meant to rearrange?
$$\frac{P_1}{P_2}=e^{-\frac{(Z_2 - Z_1)}{\lambda}}$$

Also, what are you differentiating?

3. Jan 19, 2012

### annalise17

Hmm I may not be differentiating anything actually! Sorry, my maths is lacking quite a bit so I mix up my terminology. But yes, that looks right (although I have P1 and P2 the other way around, I'll check that) I didn't know how to input it on here so attempted it in linear form.

4. Jan 19, 2012

Well if that's what you were asked to rearrange (Yes I got the $P_1$ and $P_2$ mixed up :P) Then that is right.