## List of Trigonometric Identities

Trigonometric identities are formulas that involve Trigonometric functions. Trigonometry is a branch of mathematics that deals with the study of relationships between lengths and angles of triangles. The early applications of the trigonometric functions were to surveying, navigation, and engineering. These functions also play an important role in the study of all sorts of vibratory phenomena-sound, light, electricity, etc. Trigonometric Ratios Let us take a right triangle ABC as shown below. The trigonometric ratios of the angle A in right triangle ABC are defined as follows : Note that the ratios cosec A, sec A and cot A are …