Re: a simplification problem

*To*: mathgroup at smc.vnet.net*Subject*: [mg55224] Re: [mg55172] a simplification problem*From*: Murray Eisenberg <murray at math.umass.edu>*Date*: Thu, 17 Mar 2005 03:28:49 -0500 (EST)*Organization*: Mathematics & Statistics, Univ. of Mass./Amherst*References*: <200503161035.FAA23728@smc.vnet.net>*Reply-to*: murray at math.umass.edu*Sender*: owner-wri-mathgroup at wolfram.com

(This sort of question keeps popping up in mathgroup.) One answer is: ComplexExpand[(-1)^(1/3)] but that does NOT give you -1; rather it gives the principal cube root of -1, namely, 1/2 + (Sqrt[3]/2)I. So there is no good reason that (-1)^(1/3) should simplify to -1. Remember: Mathematica does not know you intended to form just real numbers here, so it wants to interpret such things in complex terms. Hui Fang wrote: > Dear All, > > My questions is simple: > How do I simplify (-1)^(1/3) to -1? > > Thanks! > > -- 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

**References**:**a simplification problem***From:*Hui Fang <fangh73@xmu.edu.cn>