Looking down from the top edge of a 20-meter high cliff, the angle of depression to a boat on the water is 60°. What is the horizontal distance between the boat and the bottom of the cliff?

Two persons are on diametrically opposite sides of a tower. They measure the angles of elevation of the top of the tower as 30° and 60° respectively. If the height of the tower is 100 m, what is the approximate distance between the two persons?

At a point on level ground, the tangent of the angle of elevation of the top of a tower is found to be 56. On walking 70 m towards the tower, the tangent of the angle of elevation of the top of the tower is found to be 98. What is the height of the tower?