Finding distance between Pittsburgh and Miami using arc length

[Gablar16]

Hey all. This seems simple enough but, my answer doesn't match the one on the textbook and I can't see where I'm doing something wrong.

The city of pittsburg its at aproximatly 40.5 degrees and miami at 25.5 of the same meridian. Find the distance between the two cities. (earth radius is 3960 miles)

my first step was to try and find the angle so I did 40.5-25.5=15

if what I did above is correct then the rest should be simple.

convert 15 degrees to radians which in my calculations is 3Pi/16

Then I used Theta= s/r to get 1485Pi/2 or aproximatly 2332 miles but the textbook gives another answer (330Pi)

ANy help?

 

[vsage]

convert 15 degrees to radians which in my calculations is 3Pi/16

Incorrect, try to calculate it again.

 

[Gablar16]

ouch! I got the right answer now. I multiply 15 by Pi/80 instead of Pi/180.

after that correction the answer is right. Thanks very much!

Edit: Tried latex but still need some practice