FullSimplify regress?

• To: mathgroup at smc.vnet.net
• Subject: [mg81416] FullSimplify regress?
• From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
• Date: Sat, 22 Sep 2007 03:31:52 -0400 (EDT)

```In Mathematica 5.2:

FullSimplify[ComplexExpand[ArcTan[Cos[Arg[z w]-Arg[z]-
Arg[w]],Sin[Arg[z w]-Arg[z]-Arg[w]]],{z,w},TargetFunctions->
{Re,Im}]]

0

In Mathematica 6.01:

FullSimplify[ComplexExpand[
ArcTan[Cos[Arg[z*w] - Arg[z] - Arg[w]],
Sin[Arg[z*w] - Arg[z] - Arg[w]]], {z, w},
TargetFunctions -> {Re, Im}]]

ArcTan[Cos[ArcTan[Re[w], Im[w]] + ArcTan[Re[z],
Im[z]] - ArcTan[Re[w]*Re[z] - Im[w]*Im[z],
Re[z*Im[w] + w*Im[z]]]],
-Sin[ArcTan[Re[w], Im[w]] + ArcTan[Re[z], Im[z]] -
ArcTan[Re[w]*Re[z] - Im[w]*Im[z],
Re[z*Im[w] + w*Im[z]]]]]

This looks like a bit of a regress to me.

Andrzej Kozlowski

```

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