Services & ResourcesWolfram ForumsMathGroup Archive

[Date Index] [Thread Index] [Author Index]

Mathematica strange behaviour finding a cubic root

• To: mathgroup at smc.vnet.net
• Subject: [mg129111] Mathematica strange behaviour finding a cubic root
• From: sergio_r at mail.com
• Date: Sun, 16 Dec 2012 01:06:45 -0500 (EST)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• Delivered-to: l-mathgroup@wolfram.com
• Delivered-to: mathgroup-newout@smc.vnet.net
• Delivered-to: mathgroup-newsend@smc.vnet.net

How can I make Mathematica provides the same answer for
(-1/2)^(2/3) = ((-1/2)^2)^(1/3) ?

What follows is a Mathematica session:

In[1]:= (-1/2)^(2/3)

           1  2/3
Out[1]= (-(-))
           2

In[2]:= N[%]

Out[2]= -0.31498 + 0.545562 I

In[3]:= ((-1/2)^2)^(1/3)

         -(2/3)
Out[3]= 2

In[4]:= N[%]

Out[4]= 0.629961


Sergio

• Follow-Ups:
  • Re: Mathematica strange behaviour finding a cubic root
    • From: Andrzej Kozlowski <akozlowski@gmail.com>
  • Re: Mathematica strange behaviour finding a cubic root
    • From: Bob Hanlon <hanlonr357@gmail.com>
  • Re: Mathematica strange behaviour finding a cubic root
    • From: Murray Eisenberg <murray@math.umass.edu>