Trigonometry is one of the most ancient subjects studied by scholars all over the world. As we have learned in Chapter 8, trigonometry was invented because its need arose in astronomy. This chapter is the continuation of the previous chapter as here the students will study the applications of trigonometry. It is used in geography, navigation, construction of maps, determining the position of an island about the longitudes and latitudes. In this chapter, students will see how trigonometry is used for finding the heights and distances of various objects, without actually measuring them. They will get introduced to the term line of sight, angle of deviation, angle of elevation, angle of depression.