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Topic: NDSolve curve - obtain single value from curve at t:=d
Replies: 3   Last Post: Aug 17, 2012 3:45 AM

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Peter Pein

Posts: 1,147
Registered: 5/4/05
Re: NDSolve curve - obtain single value from curve at t:=d
Posted: Aug 15, 2012 3:34 AM
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Am 14.08.2012 10:23, schrieb design:
> Customized annuity applet;
> I need to find the value of sol1 at t = d;
> d, age, remaining life, fundrate, (and others) are all sliders;
> Overall apples is working well
>
> d = age + remainingLife;
> eqn1 = y'[t] == fundRate/100*y[t] - annuityAmt;=E2=80=A8sol1 = y[t]/. NDSolve[{eqn1, y[age] == startValue}, y[t], {t, age, 110}];
>
> I have tried the sol1 iteration with {d,d,110} and many other approaches to no avail.
>
> Suggestions appreciated!!
>

Hi,

DSolve[{y'[t] == fundRate/100*y[t] - annuityAmt,
y[age] == startValue}, y[t], t]

--> {{y[t] -> (1/fundRate)
E^(-((age fundRate)/
100)) (100 annuityAmt E^((age fundRate)/100) -
100 annuityAmt E^((fundRate t)/100) +
E^((fundRate t)/100) fundRate startValue)}}

doesn't help?

In simple cases, try the exact solution. Even if the calculation needs a
while (not for this differential equation), it's worth it.

Peter





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