Re: Different answers in mathematica and my calculator.

*To*: mathgroup at smc.vnet.net*Subject*: [mg125598] Re: Different answers in mathematica and my calculator.*From*: Murray Eisenberg <murray at math.umass.edu>*Date*: Tue, 20 Mar 2012 02:24:23 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <201203191000.FAA01033@smc.vnet.net>*Reply-to*: murray at math.umass.edu

Everything boils down to what the value is of (-1)^(1/3), the cube-root of -1. The difference is because your calculator is brain-dead to complex numbers! Mathematica, on the other hand, knows about complex numbers. If you want to see the Cartesian form of that cube root, evaluate this: ComplexExpand[(-1)^(1/3)] The result, in input form, will be: 1/2 + (I/2)*Sqrt[3] What Mathematica is giving you is the _principal_ cube-root of -1. (This issue is one of the most frequently asked by Mathematica neophytes.) On 3/19/12 6:00 AM, Nile wrote: > 4/(3Power[2(-2)+3, (3)^-1]) > > I get -(4/3) (-1)^(2/3) in Mathematica but only -4/3 on my calculator. > > > N[Sec[8/(8 Sqrt[2])]]/Degree to get Cos^-1 of 8/(8 Sqrt[2]) and it gives me 75 deg instead of 45... > > I'm not sure what I'm doing wrong, I tried in Wolfram Alpha and it gives me the same thing. > > Thank you. > > -Francis > -- 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**:**Different answers in mathematica and my calculator.***From:*Nile <thrasher300@gmail.com>