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CBSE - X
Trigonometric Ratios and Angles
Trigonometry is the branch of mathematics that deals with the study of relationships between sides and angles of a triangle. It is derived from Greek words, Tri meaning Three , Gon means Angle and Metron means Measure.
The ratio of lengths of two sides of a right angled triangle is called a Trigonometric Ratio. There are six trigonometric ratios
- Sine of angle
or in short denoted as sinθ is the ratio of opposite to θ to the hypotenuse. - Cosine of angle θ or in short cosθ is the ratio of adjacent to θ to the hypotenuse.
- Tangent of angle θ or tanθ is the ratio of opposite side to θ to the adjacent side to θ.
- Cotangent of angle θ or cotθ is the ratio of adjacent side to θ to the opposite side to θ.
- Secant of angle θ or secθ is the ratio of hypotenuse to the adjacent side to θ.
- Cosecant of angle θ or cosecθ is the ratio of hypotenuse to the opposite side to θ.
The relationships between the trigonometric ratios are:
- sinθ =
, cosecθ = 
, sinθ x cosecθ = 1. - cosθ =
, secθ = 
, cosθ x secθ = 1. - tanθ =
, cotθ = 
, tanθ x cotθ = 1.
