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

 –sinxAnglecircumferencecomplementarycomplete rotationcongruentconjugatecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxsupplementaryterminal sidetrigontrigonometricvertex is a measure of rotation of a given ray about its initial point.

The original ray is called the  –sinxAnglecircumferencecomplementarycomplete rotationcongruentconjugatecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxsupplementaryterminal sidetrigontrigonometricvertex and the final position of the ray after rotation is called the
 –sinxAnglecircumferencecomplementarycomplete rotationcongruentconjugatecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxsupplementaryterminal sidetrigontrigonometricvertex of the angle.

Two angles that have the exact same measure are called  –sinxAnglecircumferencecomplementarycomplete rotationcongruentconjugatecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxsupplementaryterminal sidetrigontrigonometricvertex angles.

Two angles that have their measures adding to 90◦ are called  –sinxAnglecircumferencecomplementarycomplete rotationcongruentconjugatecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxsupplementaryterminal sidetrigontrigonometricvertex angles.

Two angles that have their measures adding to 180◦ are called  –sinxAnglecircumferencecomplementarycomplete rotationcongruentconjugatecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxsupplementaryterminal sidetrigontrigonometricvertex angles.

Two angles between 0◦ and 360◦ are  –sinxAnglecircumferencecomplementarycomplete rotationcongruentconjugatecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxsupplementaryterminal sidetrigontrigonometricvertex if their sum equals 360◦.

The point of rotation is called the  –sinxAnglecircumferencecomplementarycomplete rotationcongruentconjugatecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxsupplementaryterminal sidetrigontrigonometricvertex.

Angles in standard position having their terminal sides along the x-axis or y-axis are called  –sinxAnglecircumferencecomplementarycomplete rotationcongruentconjugatecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxsupplementaryterminal sidetrigontrigonometricvertex angles.

One full anticlockwise (or clockwise) rotation of OA back to itself is called one  –sinxAnglecircumferencecomplementarycomplete rotationcongruentconjugatecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxsupplementaryterminal sidetrigontrigonometricvertex.

If the direction of rotation is anticlockwise, the angle is said to be  –sinxAnglecircumferencecomplementarycomplete rotationcongruentconjugatecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxsupplementaryterminal sidetrigontrigonometricvertex.

If the direction of rotation is clockwise, then the angle is  –sinxAnglecircumferencecomplementarycomplete rotationcongruentconjugatecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxsupplementaryterminal sidetrigontrigonometricvertex.

One sixtieth of a degree is called a  –sinxAnglecircumferencecomplementarycomplete rotationcongruentconjugatecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxsupplementaryterminal sidetrigontrigonometricvertex.

One sixtieth of a minute is called a  –sinxAnglecircumferencecomplementarycomplete rotationcongruentconjugatecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxsupplementaryterminal sidetrigontrigonometricvertex,.

There is another unit for measurement of an angle, called the  –sinxAnglecircumferencecomplementarycomplete rotationcongruentconjugatecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxsupplementaryterminal sidetrigontrigonometricvertex measure.

The  –sinxAnglecircumferencecomplementarycomplete rotationcongruentconjugatecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxsupplementaryterminal sidetrigontrigonometricvertex of a circle of radius 1 unit is 2π.

One  –sinxAnglecircumferencecomplementarycomplete rotationcongruentconjugatecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxsupplementaryterminal sidetrigontrigonometricvertex =180°/π.

All angles which are integral multiples of π/2 are called  –sinxAnglecircumferencecomplementarycomplete rotationcongruentconjugatecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxsupplementaryterminal sidetrigontrigonometricvertex angles.

 –sinxAnglecircumferencecomplementarycomplete rotationcongruentconjugatecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxsupplementaryterminal sidetrigontrigonometricvertex = 0 implies x = nπ, where n is any integer

cos (– x) =  –sinxAnglecircumferencecomplementarycomplete rotationcongruentconjugatecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxsupplementaryterminal sidetrigontrigonometricvertex

sin (– x) =  –sinxAnglecircumferencecomplementarycomplete rotationcongruentconjugatecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxsupplementaryterminal sidetrigontrigonometricvertex

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

Equations involving trigonometric functions of a variable are called  –sinxAnglecircumferencecomplementarycomplete rotationcongruentconjugatecosxgeneral solutioninitial sidemetronminutenegativepositiveprincipal solutionsquadrantalradiansecondsinxsupplementaryterminal sidetrigontrigonometricvertex equations.

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