Trigonometry is the study of the relationship between the sides and the angles of the triangle. The word trigonometry is derived from the Greek words ‘tri’ meaning three, ‘gon’ meaning sides, and ‘metron’ meaning measure.
The angle measured in an anticlockwise direction is taken as the positive angle. The angle measured in a clockwise direction is taken as the negative angle.
The ratio of the sides of the right triangle with respect to the acute angles is called the trigonometric ratio of the angle.