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Re: Cube root of -1 and 1


Bob F wrote:

> 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 ??

Branch cut and principal root are the key words here. See,

"How do I get x^(1/3) (where x is a negative number) to evaluate to a 
real number?"

http://support.wolfram.com/mathematica/mathematics/algebra/realpower.html

Regards,
-- Jean-Marc


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