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Principal Value integral


The following Principal Value integral does not appear to give the 
correct result.

Integrate[1/(x^3-1), {x, -Infinity, Infinity}, PrincipalValue->True]

This gives I Pi / 3, which surely can't be right since the answer should 
be real.

When doing it numerically, it gives the right answer:

<<NumericalMath`CauchyPrincipalValue`
CauchyPrincipalValue[1/(x^3-1), {z, -Infinity, {1}, Infinity}]

This gives -1.8138 which is the correct answer (it's -Pi/Sqrt[3]).

Any explanations? Is this a bug or am I missing something?

Carlo


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