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

*To*: mathgroup at smc.vnet.net*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)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-outx@smc.vnet.net*Delivered-to*: mathgroup-newsendx@smc.vnet.net*References*: <20140201055416.D6FE16A13@smc.vnet.net>

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