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Question: plotting functions of solutions of an ODE system & solving equations whith them

Question:plotting functions of solutions of an ODE system & solving equations whith them

apdstb 28 Maple
plot interface
May 31 2007
0
Hello!

I use Maple 9 for some weeks and it helps me a lot. In the last days I have 2 problems that I could not implement in Maple. I spent many hours reading manuals, tips etc. without finding an idea, so I decided to post here my questions:

I use dsolve (numeric) to solve a system of ODEs. I receive the solution "p" wich I can plot whithout problems.

Question 1
----------

After this, I define a new function "S" as:

S := t -> p(t)[2] + p(t)[3] + p(t)[4] + p(t)[5];

I tried to plot it with

e:=1.5;
interface(plotoutput="sum.ps");
plot(S, 1..e);

but I receive the message

Warning, unable to evaluate the function to numeric values in the region; see the plotting
command's help page to ensure the calling sequence is correct
Error, empty plot

The function "S" is defined in that region, and I can read some values, when I give e.g.:

S(1);

How could I plot this function?

Question 2
----------

I define a function and an equation as:

PH := t -> p(t)[4] + 2*p(t)[5];
phase:= PH(t)=t;
fsolve(phase, t);

But this gives me the message:

Error, (in fsolve/Iterators) not implemented yet 4

Is there a solution to this?

I would be grateful for any help.

Alexandros
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