I've encountered a problem while trying to use the answer from a NDSolve in two separate plot commands. To illustrate the problem, I'll use a simple differential equation and only one plot command. If I write something like this:
{Plot[x[t], {t, 0, 10}], x[4]}
/. NDSolve[{x'[s] == - x[s], x[0] == 1}, x, {s, 0, 10}]
It solves the equation and calculates x[4] with no problem, but the plot turns empty, and I have no idea why.
In my actual problem, my equation is a quite complicated system for several functions, and instead of x[4] I draw a parametric plot of the solved functions. I ultimately intend to include all this in a Manipulate statement so I don't want the NDSolve statement to appear more than once (takes too long) and I can't just calculate it in advance (since it has a lot of parameters).
Edit: I would like to clarify and expand my question: What I actually want to do is to include my plotting statement in a Manipulate statement in the following way:
Manipulate[{Plot[x[t], {t, 0, 10}], x[4]}
/. NDSolve[{x'[s] == - a*x[s], x[0] == 1}, x, {s, 0, 10}]
,{{a,1},0,5}]
Since only the Manipulate statement gives value to the parameter a, I can't calculate the answer to the NDSolve beforehand. Also, since my actual equation system is very complicated and non-linear, I can't use the symbolic function DSolve.
Sorry if it wasn't clear before.