By using an infinite series of rectangles in a geometric progression, Fermat found a method relate the limit of this series to the integral of [math]y=x^k[/math] for [math]k\in\mathbb{Q}^+[/math].[br][br]Increase the number of rectangles by using the slider for [i]n[/i]. The numerical approximation will tend to the integral as the slider for [math]r\rightarrow1[/math].