a lighthouse is 10 miles northwest of a dock. a ship leaves the dock at 9 am and streams west at 12 miles per hour. At what time will it be 8 miles from the lighthouse?

a lighthouse is 10 miles northwest of a dock. a ship leaves the dock at 9 am and streams west at 12 miles per hour. At what time will it be 8 miles from the lighthouse?

use law of cosines

have you made a sketch? probably the most important thing you can do to solve this problem.

the closest distance to the lighthouse will be a bit over 7 miles ... it will be a distance of 8 miles from the lighthouse at two different times.