and °. If one ship is exactly behind the other on the same side of the lighthouse, find the distance between the two ships. . A .
m tall girl spots a balloon moving with the wind in a horizontal line at a height of . m from the ground. The angle of elevation of the balloon from the eyes of the girl at any instant is °. After some time, the angle of elevation reduces to ° (see Fig.
. ). Find the distance travelled by the balloon during the interval. .
A straight highway leads to the foot of a tower. A man standing at the top of the tower observes a car at an angle of depression of °, which is approaching the foot of the Fig. . Fig.
. tower with a uniform speed. Six seconds later, the angle of depression of the car is found to be °. Find the time taken by the car to reach the foot of the tower from this point.
. Summary In this chapter, you have studied the following points : . (i) The line of sight is the line drawn from the eye of an observer to the point in the object viewed by the observer. (ii) The angle of elevation of an object viewed, is the angle formed by the line of sight with the horizontal when it is above the horizontal level, i.e., the case when we raise our head to look at the object.
(iii) The angle of depression of an object viewed, is the angle formed by the line of sight with the horizontal when it is below the horizontal level, i.e., the case when we lower our head to look at the object. . The height or length of an object or the distance between two distant objects can be determined with the help of trigonometric ratios.