ArcTan[-Infinity, y] always returning 0?

*To*: mathgroup at smc.vnet.net*Subject*: [mg69839] ArcTan[-Infinity, y] always returning 0?*From*: exogen at gmail.com*Date*: Mon, 25 Sep 2006 03:52:56 -0400 (EDT)

Hi all, I'm a little confused about the output I'm getting from ArcTan. According to this page about special values for ArcTan: http://functions.wolfram.com/ElementaryFunctions/ArcTan2/03/01/01/0005/ then: ArcTan[-Infinity, y] == (2 UnitStep[Re[y]] - 1) Pi However, when I use ArcTan where x is -Infinity, it always returns 0: In[7]:= ArcTan[-Infinity, 1] Out[7]= 0 Shouldn't this return Pi? The supposed equivalence returns the expected value: In[11]:= (2 UnitStep[Re[1]]-1) Pi Out[11]= Pi Anyone know what's going on? Thanks!