Question 3 The first ve triangular numbers are shown, where n represents the number of dots in the base of the figure, and d (n) represents the total number of dots in the figure. 1 3 6 10 15 When n = 1, there is 'l dot. When n = 2, there are 3 dots. When n = 3, there are 6 dots. Notice that the total number of dots d(n) increases by n each time. Use induction to prove that d(n) = "("2\")