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Cube root of -1 and 1

• To: mathgroup at smc.vnet.net
• Subject: [mg90875] Cube root of -1 and 1
• From: Bob F <deepyogurt at gmail.com>
• Date: Sun, 27 Jul 2008 02:32:16 -0400 (EDT)

Could someone explain why Mathematica evaluates these so differently?

In[53]:=

(Sqrt[36] - 7)^(1/3)
(Sqrt[36] - 5)^(1/3)

Out[53]= (-1)^(1/3)

Out[54]= 1

In other words why isn't (-1)^1/3 expressed as -1 ??

Thanks...

-Bob

• Follow-Ups:
  • Re: Cube root of -1 and 1
    • From: Andrzej Kozlowski <akoz@mimuw.edu.pl>
  • Re: Cube root of -1 and 1
    • From: Murray Eisenberg <murray@math.umass.edu>