# Thread: Rearranging an equation with a cosine

1. ## Rearranging an equation with a cosine

I have an equation that calculates the distance between two coordinates on Earth. The problem is, I need to rewrite this equation to solve for a different variable.

D=Distance in feet
X=Person's longitude
Y=Person's latitude
A=Some place's longitude
B=Some place's latitude

D=5280*(SQRT( (69.1*(B-Y))^2 + (69.1*(A-X)*COS(Y/57.3)) ))

How can I rearrange this equation to solve for A not D?

Thanks

2. First 2 steps are.

Divide both sides by 5280.

After that, square both sides.

Now show me some work..

I will then help some more.

3. I'll raise you the next three steps (subtracting, dividing, then adding) if you check my work!

A = ( (((D/5280)^2)-((69.1*(B-Y))^2)) / 69.1*COS(Y/57.3) ) + X

I was really intimidated with this because of the giant square root sign, and the COS which I haven't used before. But once I did the first two steps, it just unraveled for me. I hope I did it right.