(a) Use the following definition to find an expression for the area under the curve y = x3 from 0 to 3 as a limit.
The area A of the region S that lies under the graph of the continuous function f is the limit of the sum of the areas of approximating rectangles:
A = lim n → ∞ Rn = lim n → ∞ [f(x1)Δx + f(x2)Δx + . . . + f(xn)Δx]
