Given :
A sailor is 30 m above the water in the crow's nest on a sailboat.
The sailor encounters an orca surface at an angle of depression of 15 degrees.
The crows nest is 20 m horizontally from the bow (front) of the boat.
To Find :
How far in front of the boat is the orca.
Solution :
Let, distance of boat front from the crow's nest is x.
So,
[tex]\dfrac{30}{20+x}=tan \ 15^{\circ}\\\\x=\dfrac{30}{tan \ 15^{\circ}}-20\\\\x=111.94-20\\\\x=91.94\ m[/tex]
Hence, this is the required solution.