PolyLog help

*To*: mathgroup at smc.vnet.net*Subject*: [mg73689] PolyLog help*From*: Jude Bowyer <j.bowyer at ucl.ac.uk>*Date*: Sat, 24 Feb 2007 02:27:57 -0500 (EST)

Hi all, Does anyone know how Mathematica evaluates this function? As far as I understood, the dilogarithm function PolyLog[2,z] is a series like sum^{infinity}_{k=1} (z^k)/(k^2) where k is a positive integer and |z| <= 1. Mathematica returns to me a function PolyLog[2,-5R] in something I am trying to analyse, where 0 < R <= 1.. but when I plot in this range it produces a convergent output, whereas I would expect it to be divergent (and hence unplottable) beyond R = 0.2 Does anyone know how Mathematica does this?