Hello, qbkr21!
A ship is sailing due north.
At a certain point the bearing of a lighthouse is
and the distance is 12.5 (miles?)
After a while, the captain notices that the bearing of the lighthouse is now
.
How far did the ship travel between the two observations of the lighthouse? Code:
B *
| *
| *
|42.9°*
| *
c| *
| 88.5°* C
| *
|48.6°* b=12.5
| *
A *
At
the ship takes a bearing of the lighthouse at 
. . and finds angle
and
miles.
Later at point
, they find that angle
.
. . Hence, angle 
To find side
, use the Law of Sines: . 
So we have: . 
Therefore, the distance is about
miles.