public void YZ_Definition()
			{
				var value = new Vector3(23,49,73);
				var expected = new Vector2(49,73);
				Assert.AreEqual(expected, value.YZ());
			}
        public void TestVector3YZ()
        {
            // Arrange.
            var u = new Vector3(X, Y, Z);

            // Act.
            var v = u.YZ();

            // Assert.
            Assert.AreEqual(Y, v.x);
            Assert.AreEqual(Z, v.y);
        }