Using recursion to sum numbers

Question

I have just been studying the concept of recursion and I thought that I would try a simple example. In the following code, I am attempting to take the numbers: 1, 2, 3, 4, 5, an

Answer 1

        static int Sum(int[] addends)
    {
        if (addends.Length == 1)
        {
            return addends[0];
        }
        else
        {
            int tailIndex = addends.Length - 1;
            var subArray = addends[0..tailIndex];
            return addends[tailIndex] + Sum(subArray);
        }


    }