From the top of a lighthouse, an observer looking at a ship makes angle of depression of 60°. If the height of the lighthouse is 90 metre, then find how far the ship is from the lighthouse. (√3 =1.73)

Let C represent position of ship and AB represent height of the light house
Given AB = 90m
Angle of depression DAC = 60˚
Here BCAD.
BCA = DAC [Alternate interior angles]
BCA = 60˚
In ABC tan60 = AB/BC
√3 = 90/BC
BC = 90/√3 = 90√3/3
= 30√3
= 30 ×1.73
= 51.9
Hence the ship is 51.9 m away from light house.