Add Cartesian2.cross

Source/Core/Cartesian2.js

@@ -406,6 +406,22 @@ Cartesian2.dot = function (left, right) {
   return left.x * right.x + left.y * right.y;
 };
 
+/**
+ * Computes the magnitude of the cross product that would result from implicitly setting the Z coordinate of the input vectors to 0
+ *
+ * @param {Cartesian2} left The first Cartesian.
+ * @param {Cartesian2} right The second Cartesian.
+ * @returns {Number} The cross product.
+ */
+Cartesian2.cross = function (left, right) {
+  //>>includeStart('debug', pragmas.debug);
+  Check.typeOf.object("left", left);
+  Check.typeOf.object("right", right);
+  //>>includeEnd('debug');
+
+  return left.x * right.y - left.y * right.x;
+};
+
 /**
  * Computes the componentwise product of two Cartesians.
  *

Specs/Core/Cartesian2Spec.js

@@ -402,6 +402,14 @@ describe("Core/Cartesian2", function () {
     expect(result).toEqual(expectedResult);
   });
 
+  it("cross", function () {
+    var left = new Cartesian2(0.0, 1.0);
+    var right = new Cartesian2(1.0, 0.0);
+    var expectedResult = -1.0;
+    var result = Cartesian2.cross(left, right);
+    expect(result).toEqual(expectedResult);
+  });
+
   it("add works with a result parameter", function () {
     var left = new Cartesian2(2.0, 3.0);
     var right = new Cartesian2(4.0, 5.0);