# the angle of depression

• Mar 4th 2013, 04:37 AM
rcs
the angle of depression
Problem:
From the lighthouse 20m above the level of the seawater, the angle of depression of a boat is 15 degrees. how far is the boat from the point of water level directly the point of observation

can anybody let me understand me the problem... im so confused with problem ... i attempted to illustrate... im confused because it says that the angle of depression of a boat.... how come a boat has an angle of depression when the lighthouse is above the sea level...

thanks a lot
• Mar 4th 2013, 01:15 PM
topsquark
Re: the angle of depression
Quote:

Originally Posted by rcs
Problem:
From the lighthouse 20m above the level of the seawater, the angle of depression of a boat is 15 degrees. how far is the boat from the point of water level directly the point of observation

can anybody let me understand me the problem... im so confused with problem ... i attempted to illustrate... im confused because it says that the angle of depression of a boat.... how come a boat has an angle of depression when the lighthouse is above the sea level...

thanks a lot

There is an angle of depression from the lighthouse but from the boat is an angle of inclination (if that's the right word) from the boat. To my mind it's a typo in the text.

-Dan
• Mar 4th 2013, 09:02 PM
ibdutt
Re: the angle of depression
Please note that the observer is at the light house so he is above the boat and is looking down at the boat that is why angle od depression. Simplification should not be a problem, the distance of the boat will come out to be 20 cot 15 degree m.
• Mar 9th 2013, 02:38 PM
HallsofIvy
Re: the angle of depression
Quote:

Originally Posted by topsquark
There is an angle of depression from the lighthouse but from the boat is an angle of inclination (if that's the right word) from the boat.

That would be an "angle of elevation". "Inclination" could be used for either depression or elevation.

Quote:

To my mind it's a typo in the text.

-Dan
It depends upon the position of the observer. If the observer is in the boat, looking up to the lighthouse, it is an "angle of elevation". If the observer is in the lighthouse, looking down at the boat, it is an "angle of depression". The problem said "From the lighthouse...."