A numerical calculation of arc length and area using some spline quasi-interpolants

In this paper, we propose two methods to approach numerically the length of curves and the area of surface of revolution created by rotating a curve around an axis. The first is based on an approximation of functions by quadratic spline discrete quasi-interpolant and calculating its exact length. The second method consists toapproximate the values of the first derivatives by those of cubic spline discrete quasiinterpolant. Those values are used to provide a quadrature formula to calculate the integral giving the length. In both methods, we prove that the order of convergence is O (h⁴). The theoretical results given in this work are justified by some numerical examples.