Re: Is this possible? Residue computation leads to complexInfinity?

*To*: mathgroup at smc.vnet.net*Subject*: [mg60735] Re: Is this possible? Residue computation leads to complexInfinity?*From*: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>*Date*: Mon, 26 Sep 2005 04:05:40 -0400 (EDT)*Organization*: The Open University, Milton Keynes, U.K.*References*: <dh5hl9$dlc$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

kiki wrote: > In[15]:= > \!\(FullSimplify[Residue[\(\[ImaginaryI]\ z\)\/\(1 - \((2 + 4\ a)\)\ z\^2 + > z\ > \^4\), \@\(a + 1\) - \@a], \ a > 0]\) > > Out[15]= > \!\(Residue[ComplexInfinity, \(-\@a\) + \@\(1 + a\)]\) > > The syntax is not correct. Try In[1]:= FullSimplify[Residue[(I*z)/(1 - (2 + 4*a)*z^2 + z^4), {z, Sqrt[a + 1] - Sqrt[a]}], a > 0] Out[1]= (I*(-1 + Sqrt[1 + 1/a]))/(8*(-1 - a + Sqrt[a + a^2])) Regards, /J.M.