Thus for the squaring of curves, an infinitely small rectangle, a product of the ordinate in the element (that is, the infinitely small segment) of the abscissa, is taken for the trapezium which has as one of its sides the infinitely small arc opposite that infinitely small segment of the abscissa; the product is then integrated in the sense that the integral is said to give the sum of the infinitely small trapezia or the surface of which the determination is being sought, namely the finite magnitude of this element of the area.