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

Abstract

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 to approximate 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(h^4). The theoretical results given in this work are justified by some numerical examples.