Trigonometry involves the relationships between the lengths and angles of triangles. It has various application such as in astronomy, in calculating the distance from Earth to the stars or planet, in navigation, to construct maps, determining the position of an island in relation to the latitudes and longitudes etc.
Heights and Distances-
The line of sight AC is from the observer to the top of the minar. The angle CAB is the angle of elevation, when an observer view from the horizontal.
The angle of depression of a point on the object being viewed from the top of a building is the angle formed by the line of sight with the horizontal.