// Convert from degrees to radians.
Math.radians = function(degrees) {
	return degrees * Math.PI / 180;
}
Math.radians(90); // 1.5707963267948966

// Convert from radians to degrees.
Math.degrees = function(radians) {
	return radians * 180 / Math.PI;
}
Math.degrees(3.141592653589793); // 180