Re: Units question

*To*: mathgroup at smc.vnet.net*Subject*: [mg115555] Re: Units question*From*: Bob Hanlon <hanlonr at cox.net>*Date*: Fri, 14 Jan 2011 06:19:43 -0500 (EST)

Dimensions aren't numbers, so being positive doesn't make sense. It is a just convenient to say that they are positive to trick Sqrt and the like. In some cases using this is better than using PowerExpand since PowerExpand would affect the treatment of variables not just the dimensions. You can handle all of the dimensions at once: Needs["Units`"] simplifyUnits = ToExpression[# <> " > 0" & /@ Names["Units`*"]]; Simplify[Sqrt[Meter^2/Second^2] Second/Meter^2, simplifyUnits] 1/Meter Bob Hanlon ---- Murray Eisenberg <murray at math.umass.edu> wrote: ============= Even after loading the Units package, Mathematica doesn't know that Meter and Second are positive. My naive sense is that this is just plain stupid. Am I missing something here? On 1/12/2011 4:07 AM, Bob Hanlon wrote: > Simplify[Sqrt[Meter^2/Second^2] Second/Meter^2, > {Meter> 0, Second> 0}] > > 1/Meter > > > Sqrt[Meter^2/Second^2] Second/Meter^2 // PowerExpand > > 1/Meter > > > Bob Hanlon > > ---- Ted Sariyski<tsariysk at craft-tech.com> wrote: > > ============= > Hi, > Working with units I get correct result: > > Sqrt[Meter^2/Second^2] Second)/Meter^2 > > How to tell Mathematica to simplify the result to Meter^-1? > Simplify and FullSimplify doesn't do the job. > Thanks in advance, > --Ted > > -- Murray Eisenberg murray at math.umass.edu Mathematics & Statistics Dept. Lederle Graduate Research Tower phone 413 549-1020 (H) University of Massachusetts 413 545-2859 (W) 710 North Pleasant Street fax 413 545-1801 Amherst, MA 01003-9305 -- Bob Hanlon

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