Re: ArcTan[-Infinity, y] always returning 0?
- To: mathgroup at smc.vnet.net
- Subject: [mg69857] Re: ArcTan[-Infinity, y] always returning 0?
- From: dh <dh at metrohm.ch>
- Date: Tue, 26 Sep 2006 00:59:12 -0400 (EDT)
- References: <email@example.com>
Hi, The Help is o.k., but the Kernel is wrong. Can't see a reason for this, looks like an error to me. I am getting zero too in Mathermatica version 5.1 Daniel exogen at gmail.com wrote: > 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:= > ArcTan[-Infinity, 1] > > Out= > 0 > > Shouldn't this return Pi? > > The supposed equivalence returns the expected value: > > In:= > (2 UnitStep[Re]-1) Pi > > Out= > Pi > > > Anyone know what's going on? > > Thanks! >