13.
A 20-foot ladder is leaning against a wall. The foot of the ladder is 7 feet from the base of the wall. What is the approximate measure of the angle the ladder forms with the ground?
15.
A man on the ground looking up at a plane, and a pilot looking down at the man on the ground. The plane is 300 metres off the ground, and the angle of depression is approximately 19 degrees. What is the angle of elevation to the nearest whole degree?
18.
A man stands at the top of a building 40 meters tall. He observers that the angle of elevation of the top of a tower, 50 meters away, is 20 degrees. What is the height of the tower?