Plotting interpolating functions

*To*: mathgroup at yoda.physics.unc.edu*Subject*: Plotting interpolating functions*From*: tim at math.earlham.edu (Tim McLarnan)*Date*: Thu, 8 Oct 92 14:09:27 EST

This is probably silly, but, For an applied math class, I'd like to plot together a function giving the external force on a damped oscillator, and the solution to the oscillator's motion. I understand that the way to plot the numerical solution is to do something like Plot[Evaluate[y[t] /.NDSolve[{y''[t]+(1/2)y'[t]+y[t] == Sin[t], y[0]==0, y'[0]==0}, y, {t,0,20}]], {t,0,20}] I therefore assumed that one could plot this function together with the driving function Sin[t] by saying something like Plot[{Sin[t], Evaluate[y[t]/.NDSolve[{y''[t]+(1/2)y'[t]+y[t]==Sin[t], y[0]==0, y'[0]==0}, y, {t,0,20}]]}, {t,0,20}] This and all attempts like it end in a blizzard of error messages. What am I doing wrong? (This is with Mma 2.1 on a NeXT.) --- Tim McLarnan tim at math.earlham.edu Dept. of Mathematics, Earlham College, Richmond, IN 47374