Trigonometry is a branch of mathematics that deals with relationships between sides and angles of triangles. The document defines trigonometric ratios like sine, cosine, and tangent that relate the sides and angles of a right triangle. It also discusses trigonometric identities, angle measurement in degrees and radians, measuring angles in different quadrants, and the values of trigonometric functions for special angles.
9. Measurement of Radian Angle subtended at the centre by an arc of length 1 unit in a unit circle is said to have a measure of 1 radian. 1 Radian 1 1 O A B 1 θ (r) l θ = l/r l = r θ