Posted by shep on .
From a point B that is 9 meters above level ground , the angle of elevation of the top of a building is 43 degrees and the angle of depression of the base of the building is 7 degrees. What is the height of the building.
(tell what formula and why you used it will very much be appreciated)

precal 
Steve,
draw a horizontal line from B to where it intersects the building wall. Call that point C.
Label the top of the building A, and the bottom D.
The height of the building is thus
AD = AC + CD
AC/BC = tan 43°
CD/BC = tan 7°
Now, you see that without knowing the distance BC, there is no way to determine the height of the building. The farther away you are, the higher the building.