Question

As observed from the top pf a lighthouse 100m above the sea level ,the angle of depression of a ship sailing directly towards it changed from 30 to 60 degree. determine the disrance travelled by the ship during the period of Observation.

Answer 1

In ∆ABC

tan60=AB/BC

✓3=100/BC

BC=100/√3

IN ∆ABD

tan30=AB/BD

1/√3=100/BD

BD=100/√3

CD=BD-BC

100√3-100/√3

300-100/√3. (TAKING LCM)

200/√3

CD=115.61m