Re: Different answers in mathematica and my calculator.

*To*: mathgroup at smc.vnet.net*Subject*: [mg125647] Re: Different answers in mathematica and my calculator.*From*: Dana DeLouis <dana01 at me.com>*Date*: Sun, 25 Mar 2012 00:16:02 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com

> 4/(3Power[2(-2)+3, (3)^-1]) > > I get -(4/3) (-1)^(2/3) in Mathematica but only -4/3 on my calculator. Hi. Depending on the math one is doing, this general idea might be a possible solution. fix = (x_)?Negative^ (Rational[a_, b_]) :> Piecewise[{{(x^a)^(1/b), EvenQ[a]}, {-((-x)^a)^(1/b), OddQ[b]}, {x^(a/b), True}}]; Here are 3 numbers: equ={ 4/(3Power[2(-2)+3,(3)^-1]) , Power[-8,2/3], Power[-27,1/3] } {-(4/3) (-1)^(2/3), 4 (-1)^(2/3), 3 (-1)^(1/3)} For something quick-n-dirty, this makes an attempt for what you want. equ /. fix {-(4/3), 4, -3} For complex numbers, the magnitude is the value, but as you can see, the sign can be wrong. For some things, that's all one might need thou. Abs /@ equ {4/3, 4, 3} = = = = = = = = = = = = HTH :>) Dana DeLouis Mac & Math 8 = = = = = = = = = = = = On Mar 19, 6:04 am, Nile <thrasher... at gmail.com> 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