It is 4.7km from Lighthouse A to Port B. The bearing of the port from the lighthouse is N73E. A ship has sailed due west from the port and its bearing from the lighthouse is N31E. How far has the ship sailed from the port?

Answer 1

If the ship has sailed to point C,
angle A = 73°-31° = 42°
angle B = 17°
so, angle C is 121°

the distance AC is side a, where

a/sin42° = 4.7/sin121°
a = 3.67