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Re: Another damn simplifying problem: ArcTan

  • To: mathgroup at smc.vnet.net
  • Subject: [mg59947] Re: Another damn simplifying problem: ArcTan
  • From: Mathieu McPhie <m.mcphie at fz-juelich.de>
  • Date: Fri, 26 Aug 2005 04:53:37 -0400 (EDT)
  • Organization: Forschungszentrum Juelich GmbH
  • References: <dek7hq$a2t$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Sorry, I got my x's and y's mixed up, and so I was more curious about 
why "M" can't simplify the following:

Simplify[ArcTan[x,-y]+ArcTan[x,y]]

This can be simplified by choosing x > 0, and not if x < 0. Which 
according to the range of the ArcTan function should also evaluate to 0.

Cheers, Mat

Mathieu McPhie wrote:
> Can someone please explain this to me: (M v4.something)
> 
> In:=  Simplify[ArcTan[-x]+ArcTan[x]]
> Out= 0
> 
> In:=  Simplify[ArcTan[-x,1]+ArcTan[x,1]]
> Out= ArcTan[-x,1]+ArcTan[x,1]
> 
> Note, I want something more complicated than this obviously. Actually 
> want something like
> 
> Simplify[ArcTan[-x,y]+ArcTan[x,y]]
> 
> but above is the easiest example of this infuriating programs problem.
> 
> Cheers, Mathieu
> 


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