Trig
posted by Chetan Munsell .
The angle of elevation to the top of a building from a point on the ground is 39 degrees. From a point 50 feet closer to the building, the angle of elevation is 48 degrees. What is the height of the building?

draw the figure. You have two triangles. let x be the distance to the closer point, from the building.
Tan48=h/x
Tan39=h/(x+50)
or
x=h/tan48 and
x=h/tan39 50
set them equal, and solve for h.