The word ‘trigonometry’ is derived from the Greek words ‘ –sinxAnglecircumferencecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxterminal sidetrigontrigonometricvertex’ and ‘ –sinxAnglecircumferencecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxterminal sidetrigontrigonometricvertex’ and it means ‘measuring the sides of a triangle’.

 –sinxAnglecircumferencecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxterminal sidetrigontrigonometricvertex is a measure of rotation of a given ray about its initial point.

The original ray is called the  –sinxAnglecircumferencecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxterminal sidetrigontrigonometricvertex and the final position of the ray after rotation is called the
 –sinxAnglecircumferencecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxterminal sidetrigontrigonometricvertex of the angle.

The point of rotation is called the  –sinxAnglecircumferencecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxterminal sidetrigontrigonometricvertex.

If the direction of rotation is anticlockwise, the angle is said to be  –sinxAnglecircumferencecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxterminal sidetrigontrigonometricvertex.

If the direction of rotation is clockwise, then the angle is  –sinxAnglecircumferencecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxterminal sidetrigontrigonometricvertex.

One sixtieth of a degree is called a  –sinxAnglecircumferencecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxterminal sidetrigontrigonometricvertex.

One sixtieth of a minute is called a  –sinxAnglecircumferencecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxterminal sidetrigontrigonometricvertex,.

There is another unit for measurement of an angle, called the  –sinxAnglecircumferencecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxterminal sidetrigontrigonometricvertex measure.

The  –sinxAnglecircumferencecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxterminal sidetrigontrigonometricvertex of a circle of radius 1 unit is 2π.

One  –sinxAnglecircumferencecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxterminal sidetrigontrigonometricvertex =180°/π.

All angles which are integral multiples of π/2 are called  –sinxAnglecircumferencecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxterminal sidetrigontrigonometricvertex angles.

 –sinxAnglecircumferencecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxterminal sidetrigontrigonometricvertex = 0 implies x = nπ, where n is any integer

cos (– x) =  –sinxAnglecircumferencecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxterminal sidetrigontrigonometricvertex

sin (– x) =  –sinxAnglecircumferencecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxterminal sidetrigontrigonometricvertex

The solutions of a trigonometric equation for which 0 ≤ x < 2π are called  –sinxAnglecircumferencecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxterminal sidetrigontrigonometricvertex.

Equations involving trigonometric functions of a variable are called  –sinxAnglecircumferencecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxterminal sidetrigontrigonometricvertex equations.

The expression involving integer‘n’ which gives all solutions of a trigonometric equation is called the  –sinxAnglecircumferencecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxterminal sidetrigontrigonometricvertex.