The angles of elevation of the top of a tower at two points, which are at distances a and b from the foot in the same horizontal line and on the same side of the tower, are complementary. The height of the tower is

1) ab

2) √ab

3) √(a/b)

4) √(b/a)  

The bell tower of the cathedral in Pisa, Italy, leans from the vertical. A tourist stands 105 m from its base, with the tower leaning directly toward her. She measures the angle of elevation to the top of the tower to be . Find the length of the tower to the nearest meter.

In San Francisco, a certain hill makes an angle of 20 degress with the horizontal and has a tall buiulding at the top. At a point 100 ft down the hill from the base of the building, the angle of elevation to the top of the building is 72 degrees. What is the height of the building?

You are stationary on the ground and are watching a bird fly horizontally towards you at a rate of −3 m/s. The bird is located 50 m above your head. How fast does the angle of elevation of your head change when the horizontal distance between you and the bird is 180 m? (Leave your answer as an exact number.)