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Bug with ComplexExpand on PolyGamma?

  • To: mathgroup at
  • Subject: [mg15148] Bug with ComplexExpand on PolyGamma?
  • From: Dirk Reiss <reiss at>
  • Date: Wed, 16 Dec 1998 03:11:22 -0500
  • Sender: owner-wri-mathgroup at


when I apply 

In[1]:= ComplexExpand[Im[PolyGamma[a + I b]]]

I get the result:

Out[1]= 0

which is obviously not true. E.g. 

In[2]:= ComplexExpand[Im[PolyGamma[1 + I 3]]] //N


Out[2]= 1.40413

is this a bug?

Dirk Reiss

Institut fuer Laser-Physik
Universitaet Hamburg

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