# Homework Help: Help with distance between cities?

1. Feb 26, 2012

### theintarnets

1. The problem statement, all variables and given/known data
Find the distance in kilometers between each pair of cities assuming they lie on the same north-south line:
Panama City, Panama, 9° N and Pittsburgh, Pennsylvania 40° N

2. Relevant equations
All we talked about in class is that θ = S/r

3. The attempt at a solution
I'm really not sure what to do... I assume I'm supposed to be solving for s or r, given that θ1 is 9 and θ2 is 40 but...I'm still not sure what to do.

2. Feb 26, 2012

### PeterO

The distance between them is along an arc - if you assume the earth is a perfect sphere - we commonly do.

3. Feb 26, 2012

### theintarnets

So what am I supposed to do? All I'm given is 9 and 40. I know I need S or R, but I don't know how to get them.

4. Feb 26, 2012

### theintarnets

Nevermind, I think I've got it. Apparently the radius of Earth is 6400 km. So I converted the given θ's to radians and then solved for S for the both of them, then subtracted to get the distance between the two :D Thanks for the hint, PeterO