## NCERT Solutions for Class 10th Maths Chapter 9 Exercise 9.1 Question 2  NCERT Solutions for maths in Video https://www.youtube.com/user/cbsepapers/videos
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In the previous chapter, you have studied about trigonometric ratios. In this chapter,  you will be studying about some ways in which trigonometry is used in the life around  you. Trigonometry is one of the most ancient subjects studied by scholars all over the  world. As we have said in Chapter 8, trigonometry was invented because its need  arose in astronomy. Since then the astronomers have used it, for instance, to calculate  distances from the Earth to the planets and stars. Trigonometry is also used in geography  and in navigation. The knowledge of trigonometry is used to construct maps, determine
the position of an island in relation to the longitudes and latitudes.

In This Chapter. You have studied The Follwing Points:
1. (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.
2. The height or length of an object or the distance between two distant objects can be  determined with the help of trigonometric ratios.