Area Calculation in C#

AreaCalc.cs

using System;

namespace DistanceAreaCalc {
	class GeoCoordinate{
		public double Longitude;
		public double Latitude;
		public GeoCoordinate(double lat, double lng) {
			this.Latitude = lat;
			this.Longitude = lng;
		}
	}

	class MainClass {
		public static void Main (string[] args) {
			double area = GetArea(new GeoCoordinate[]{
				new GeoCoordinate(40.76822,-73.981567),
				new GeoCoordinate(40.76439,-73.97308),
				new GeoCoordinate(40.796787,-73.949398),
				new GeoCoordinate(40.800654,-73.958248),
				new GeoCoordinate(40.76822,-73.981567)
			});
			Console.WriteLine(area/1000000 + " km^2");
		}
		public static double Rad(double deg){
			return deg * Math.PI / 180.0f;
		}
		public static double GetArea(GeoCoordinate[] coords){
			var area = 0.0;
			var len = coords.Length;
			if (len > 2){

				for (var i = 0; i < len - 1; i++){
					GeoCoordinate p1 = coords[i];
					GeoCoordinate p2 = coords[i + 1];
					area += Rad(p2.Longitude - p1.Longitude) * (2 + Math.Sin(Rad(p1.Latitude)) + Math.Sin(Rad(p2.Latitude)));
				}
				area = area * 6378137.0 * 6378137.0 / 2.0;
			}
			return Math.Abs(area);
		}
	}
}