As observed from the top of a light house, 120√3 m above the sea level, the angle of depression of a ship sailing towards it changes from 30º to 60º. The distance travelled by the ship during the period of observation is :
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 240 m
Concept
Basic Trigonmetric rations and trignometric values
Application
In triangle ABD
tan60° = AB/BD
Putting the value of tan60° = √3 , we get
√3 = 120√3 / BD
BD = 120 m
In ΔABC,
tan 30° = AB/BC
Putting the value of tan 30° = 1/√3
1/√3 = 120√3/BC
BC = 360
DC = BC - BD
DC = 360 - 120
DC = 240 m