INTRODUCTION:

Trigonometry can be used in many ways in the things around us, like we can use it for calculating the height and distance of some objects without calculating them actually.

Let O and P be two points such that the point P is higher level let OA and PB be horizontal lines through O and P respectively. If an observer is at O and the point P is the object to be seen then the line OP is, called the line of sight of the point P and the  ∠AOP, between the lines of the sight and the horizontal line OA, is called as the angle of elevation of point P as it is seen from point O.

If an observer is at P and the object to be seen is at O, then the  ∠BPO is known as the angle of depression of O as seen from P.

So, we can say that the angle of elevation of a point P as seen from a point O is equal to the angle of depression of O as seen from P.

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.