using System.Numerics; // Declare two vectors Vector3d a = new Vector3d(1, 2, 3); Vector3d b = new Vector3d(4, 5, 6); // Add the two vectors Vector3d c = Vector3d.Add(a, b); // Display the result Console.WriteLine("c = ({0}, {1}, {2})", c.X, c.Y, c.Z);In the above example, we declare two vectors `a` and `b` with coordinates (1, 2, 3) and (4, 5, 6) respectively. We then add these vectors using the Vector3d Add function and store the result in vector `c`. Finally, we display the values of vector `c`. The Vector3d Add function is part of the System.Numerics.Vectors package in C#. This package provides a set of vector-related classes, such as Vector2, Vector3, Vector4, etc., that can be used for efficient and easy manipulation of vectors in mathematical calculations and graphics programming.