Radian Angles

When working with trigonometric functions in JavaScript the units have to be in radians and not in degrees. Radians are a standard unit of angular measurement. A radian is the angle that is swept out when the radius of a circle and the swept out arc length are equal in length.


Figure 1 One Radian

A complete circle, 360º, is equivalent to 2π radians. Thus the conversion from degrees to radians is as follows:


The conversion from radians to degrees is as follows:



The conversion between degrees and radians will be used often. Knowing this we will create two functions that will convert from degrees to radians and back again.

function DegtoRad(x){
 return x*Math.PI/180;

function RadtoDeg(x){
 return x*180/Math.PI;

Listing 1 Conversion function for radians and degrees


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