Date: Jan 10, 2013 2:20 AM
Author: Abed Alnaif
Subject: Manipulate: Tracking symbols which are not stated explicitly

Hello,
I am trying to use the Manipulate command to adjust symbols which are not stated explicitly within the command. Is this possible? I am using Mathematica 7.0.1.0. Consider these examples:

The code below works:

Manipulate[
reprule = {end -> endval};
NDSolve[{y''[x] + Sin[y[x]] y[x] == 0, y[0] == 1, y'[0] == 0},
y, {x, 0, end} /. reprule], {endval, 10, 20}]

However, this one tells me that "Endpoint endval is not a real number":

reprule = {end -> endval};
Manipulate[
NDSolve[{y''[x] + Sin[y[x]] y[x] == 0, y[0] == 1, y'[0] == 0},
y, {x, 0, end} /. reprule], {endval, 10, 20}]