Re: Possible Bug in ArcTan ?

*To*: mathgroup at smc.vnet.net*Subject*: [mg64784] Re: Possible Bug in ArcTan ?*From*: "Jens-Peer Kuska" <kuska at informatik.uni-leipzig.de>*Date*: Thu, 2 Mar 2006 19:28:04 -0500 (EST)*Organization*: Uni Leipzig*References*: <du6o44$5rg$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Hi, why can ArcTan[] have two arguments ArcTan[x,y] ... Regards Jens "JCDenton" <post4uw at web.de> schrieb im Newsbeitrag news:du6o44$5rg$1 at smc.vnet.net... | Hi Group! | | I am describing resonant electrical systems with Mathematica. So there | is a lot of dealing with complex numbers and functions. One important | function is: | | phi=ArcTan[Im/Re] | | This function is zero when Im = 0. The problem is, that when I plot | this function it shows some strange behaviour near this zero point. It | looks somehow, as if the function values are multiplied with -1 or | something like that. I also tried to calculate a table an plot this | with gnuplot where the stepsize was 0.005. I was the same strange | situation. So I am sure it is not the Plot function that is buggy but | the ArcTan itself. I also tried the table with step size 0.05 and I get | the "right" picture with gnuplot. Is this a known bug? I have not found | something about it yet. | | I realy need this function, since it is a very important operation in | complex calculation. | | Thank you! |