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Re: Result to DEQ with WA versus Step-by-Step Yields Different Result

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  • Subject: [mg132298] Re: Result to DEQ with WA versus Step-by-Step Yields Different Result
  • From: Murray Eisenberg <murrayeisenberg at gmail.com>
  • Date: Mon, 3 Feb 2014 05:16:12 -0500 (EST)
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The full solution, shown by WolframAlpha, or obtained directly in Mathematica from

soln = Expand[v[t] /.
First@DSolve[{v''[t] + 10 v'[t] + 125 v[t] == 250 UnitStep[t],
   v[0] == 0, v'[0] == 25}, v[t], t]]

reduces when t > 0 to that shown in the step-by-step solution, as Mathematica also can show:

 Simplify[soln, t>0]

So not a bug, just a design decision as to what is to be shown.


On Feb 1, 2014, at 12:54 AM, amzoti <amzoti at gmail.com> wrote:

> When you solve this DEW using WA, you get a result.
>
> However, when you click step-by-step, the result is different.
>
> Is this a bug?
>
> v'' + 10 v' + 125 v = 250 unitstep(t), v(0) = 0, v'(0) = 25


Murray Eisenberg                                murray at math.umass.edu
Mathematics & Statistics Dept.      
Lederle Graduate Research Tower      phone 240 246-7240 (H)
University of Massachusetts               
710 North Pleasant Street                
Amherst, MA 01003-9305









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