Trigonometry

Trigonometry is the study of relationships between the sides and angles of a triangle. The earliest known work on trigonometry was recorded in Egypt and Babylon. Early astronomers used it to find out the distances of the stars and planets from the Earth. Even today, most of the technologically advanced methods used in Engineering and Physical Sciences are based on trigonometrical concepts.

Ratios of the sides of a right triangle with respect to its acute angles called trigonometric ratios of the angle.We will restrict our discussion to acute angles only. However, these ratios can be extended to other angles also. We will also define the trigonometric ratios for angles of measure 0° and 90°. We will calculate trigonometric ratios for some specific angles and establish some identities involving these ratios, called trigonometric identities.

The trigonometric ratios of the angle A in right triangle ABC are defined as follows :

sin A = opposite / hypotenuse = a / c

cos A = adjacent / hypotenuse = b / c

tan A = opposite / adjacent = a / b

csc A = hypotenuse / opposite = c / a

sec A = hypotenuse / adjacent = c / b

cot A = adjacent / opposite = b / a