Want to show: the sum of the first n natural numbers equals n(n+1)/2

We know that the statement is true for arbitrary n, so the sum of the first n natural numbers is n(n+1)/2. However, since n is arbitrary we should consider some different cases to account for varying properties of n

We know that the statement is true for arbitrary n, so the sum of the first n natural numbers is n(n+1)/2. We should add n+1 to this to get a new formula for the sum of the first n+1 natural numbers.