The word ‘trigonometry’ is derived from the Greek words ‘tri’ (meaning three), ‘gon’ (meaning sides) and ‘metron’ (meaning measure). In fact, trigonometry is the study of relationships between the sides and angles of a triangle.
Application of Trigonometry:
Find height of tall building or tower without actually measuring it
Find the height at which an object , airplane or balloon is flying
Find the distance of a vehicle or ship from a tower.
Used extensively in the field of construction.
Determine position of a place in a Map using latitude & Longitude
Astronomers use it to calculate distances from the Earth to the planets and stars.
Angle of Elevation & Depression
The line of sight is the line drawn from the eye of an observer to the point in the object viewed by the observer.
The angle of elevation of the point viewed is the angle formed by the line of sight with the horizontal when the point being viewed is above the horizontal level, i.e., the case when we raise our head to look at the object.
The angle of depression of a point on the object being viewed is the angle formed by the line of sight with the horizontal when the point is below the horizontal level, i.e., the case when we lower our head to look at the point being viewed.
Numerical: The angle of elevation of the top of a tower from a point on the ground, which is 30 m away from the foot of the tower, is 30°. Find the height of the tower.