Re: Problems integrating InterpolatingFunction

*To*: mathgroup at smc.vnet.net*Subject*: [mg116056] Re: Problems integrating InterpolatingFunction*From*: Roland Franzius <roland.franzius at uos.de>*Date*: Mon, 31 Jan 2011 03:23:31 -0500 (EST)*References*: <ii2c82$ra6$1@smc.vnet.net>

Am 30.01.2011 01:43, schrieb Sergio Miguel Terrazas Porras: > Hello group, > > I use NDSolve for a nonlinear differential equation, and I get an InterpolatingFunction, as expected. > > I can plot it, evaluate it, etc. > > The problem I have is that now I need to integrate 1/(the square of the InterpolatingFunction), and I get nothing but the input back. > > Any ideas? > > Thanks in advance. > > Sergio Terrazas > Yoy can integrate InterpolatingFunction explitely using Derivative of negative order eg the critical soltion to the equations of motion of an anharmonic pendulum X[t_] = x[t] /. NDSolve[{x''[t] == -x[t]^3 + x[t], x'[0] == 0, x[0] == 1.42}, x[t], {t, 0, 100}] // First Y[t_]=Derivative[-1][Y][t] -- Roland Franzius