Convert degrees <-> radians. Taken from Google Closure lib.

degrees-radians.js

/**
 * Converts degrees to radians.
 * @param {number} angleDegrees Angle in degrees.
 * @return {number} Angle in radians.
**/
function degreesToRadians(angleDegrees) {
  return angleDegrees * Math.PI / 180;
}

/**
 * Converts radians to degrees.
 * @param {number} angleRadians Angle in radians.
 * @return {number} Angle in degrees.
**/
function radiansToDegrees(angleRadians) {
  return angleRadians * 180 / Math.PI;
}