Calculations with Interpolating Functions

*To*: mathgroup at smc.vnet.net*Subject*: [mg88470] Calculations with Interpolating Functions*From*: João Paulo Casquilho <jp at fct.unl.pt>*Date*: Tue, 6 May 2008 06:39:26 -0400 (EDT)

Hi I obtain an Interpolating function as a solution of a differential equation with the command NDSolve, lets call it =93solution=94, which gives x(t). Next I want to use this solution for further calculations. With the commands =93result=Evaluate[x(t)/. First[solution]]=94 or =93result= x(t)/.solution, {t,0,tmax}=94 I do the plot x(t) without any problems. Now, with version 5.2 I manage to integrate x(t) or linear functions of it. But when I try to integrate non linear functions of x(t), like x(t)^2 or Sin[x(t)] (which is what I want), Mathematica is unable to give a numerical result, all I get is an integral saying that there is an InterpolatingFunction in the integrand. With Mathematica 6 the linear integration does not work either. Any help would be appreciated. Best Regards Joao Paulo