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Numerical Diff. EQ. Solver not working.

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Reffu

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Feb 6, 2012, 2:35:41 PM2/6/12
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I'm probably doing something wrong, but I wanted to test out an equation in the solver under NUM.SLV>diff eq.
I entered my equation on the top '2*X^2+Y^3'
indep: X init:1 Final:2
Soln: Y init:2 Final:
Tol:.0001 Step:dflt

When I hit solve, it sat there for several minutes before I stopped. It was thinking the whole time but I'm not sure what it was doing. I was just wondering if this was a bug or if I forgot to set a flag correctly. Also, if I enter step:1 would it give me a solution as if I had use Euler's method?

Thanks,
Reffu

electricpete

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Feb 6, 2012, 9:31:24 PM2/6/12
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On Feb 6, 1:35 pm, Reffu <nickmarshal...@gmail.com> wrote:
> I entered my equation on the top '2*X^2+Y^3'
> indep: X init:1 Final:2
> Soln:  Y init:2 Final:

Have you tried to simulate that on another platform? I think it may
"blow up" before X gets to 2.

electricpete

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Feb 6, 2012, 10:07:09 PM2/6/12
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Here are some values of the solution that I got by starting with a low
value for Xfinal and slowly increasing:
(X ,Y)
(1 , 2)
(1.05,2.7)
(1.1,6)
(1.11, 11)
(1.112, 18)
(1.113, 31)
(1.1135,185)
(1.114.... calculator hourglass remains for longer than I care to
wait).
Note the independent variabel X points above are not equally spaced,
but getting closer together.
It seems pretty clear the solution blows up around 1.115.


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