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Simplification and Arg[]

• To: mathgroup at smc.vnet.net
• Subject: [mg66593] Simplification and Arg[]
• From: Andrew Moylan <andrew.moylan at anu.edu.au>
• Date: Sun, 21 May 2006 22:30:37 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

Should Mathematica be able to simplify the following expression? (It is 
easily seen to be zero under the given condition, x > 0.)

FullSimplify[
	Arg[1 + I * x] + Arg[1 - I * x],
	{x > 0}
]

In particular, I would have expected the following to yield ArcTan[b / 
a], from which the above expression is easily reduced to zero:

FullSimplify[
	Arg[a + I b],
	{a > 0, b > 0}
]

Any ideas?

Cheers,

Andrew

P.S. Apologies if I have sent this twice; my original message seems not 
to have worked.

• Follow-Ups:
  • Re: Simplification and Arg[]
    • From: Andrzej Kozlowski <akoz@mimuw.edu.pl>