What is trigonometry

What is trigonometry Tri means three, gon means side and metry means measurement. Measurement of three sides is the Trigonometry. Hence in Trigonometry we deal with triangles. When two angles of a triangle were given then the third side of it can be calculated by using the theorem Sum of all angles in a triangle is 180. When the length of two sides is given then the range of third side can be calculated. Here in most of the cases a right angled triangle is used. Pythagoras theorem is c = a + b All the trigonometric ratios (sin, cos, tan, cosec, sec, cot) are defined by using a right angled triangle. Some of the trigonometric identities are also defined. sin a + cos a = 1 sec a - tan a = 1 csc a - cot a = 1 Sum and difference formulae: Sin ( x + y) = sin x cos y + cos x sin y Sin (x y) = sin x cos y cos x sin y Cos (x+ y) = cos x cos y sin x sin y Cos (x y) = cos x cos y + sin x sin y