Posted by **pooja** on Tuesday, November 8, 2011 at 4:14am.

from the top of a light house the angle of depression of a ship sailing towards it was found to be 30 degrees . after 10 seconds the angle of depresion changes to 60 degrees. assuming that the ship is sailing at uniform speed. find how much time it will take to reach the light house?

- maths -
**Steve**, Tuesday, November 8, 2011 at 12:59pm
Locate points on the ocean:

Let the point at 30 degrees be A

Let the point at 60 degrees be B

Let the base of the lighthouse be point C

Let the height of the lighthouse be h

h/BC = tan 60 = √3

h/AC = tan 30 = 1/√3

√3 BC = 1/√3 AC

3BC = AC

That means AC = AB + BC

SO, 3BC = AB + BC

So, AB = 2BC

AB was traveled in 10 seconds.

So, BC will take only 5 seconds to cover.

Watch out for those rocks!

## Answer This Question

## Related Questions

- Pre Calc - from the top of a 250 ft lighthouse the angle of depression to a ship...
- Maths - An observer at the top of a lighthouse 55m Hugh sights a ship at a sea ...
- Geometry - A ship is 750 meters from a light house which is 50 meters tall. What...
- Maths - A ship is sighted from the top of a lighthouse. The angle of depression ...
- trigonometry - From a window 20m above the ground, a person could see the top of...
- Geometry - There is a flagpole in the school parking lot. Which of the ...
- Calculus - A ship sailing parallel to shore sights a lighthouse at an angle of ...
- maths - a person observed from the top of a light house which is 80 m above the ...
- math - the Angle of Elevation From a Ship to the Top of a Lighthouse on the ...
- maths-urgently needed - From the top of a tower the angle of depression of an ...

More Related Questions