Help with distance between cities?

[theintarnets]

Homework Statement

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

Homework Equations

All we talked about in class is that θ = S/r

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.

 

[PeterO]

Homework Statement

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

Homework Equations

The Attempt at a Solution

I'm really not sure what to do...

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

 

[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.

 

[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