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Re: simplify Arg[E^(I x)]?
The first and obvious problem is that it should be FullSimplify and not Fullsimplify. But fixing that won't help since your expected answer is incorrect. All you need to do is to look up Mathematica's help for Arg and you will see: The result from Arg[z] is always between -\[Pi] and +\[Pi] But then, it is immediately obvious that if you take an x not in this range than the answer is not going to be x, for example: Arg[Exp[3 Pi/2 I]] -(\[Pi]/2) Also, this tells you what you have to do to get the answer you are looking for: FullSimplify[Arg[Exp[I x]], -Pi < x <= Pi] x Andrzej Kozlowski On 31 Mar 2012, at 10:42, Neal Becker wrote: > Why doesn't this simplify? > > Fullsimplify[Arg[E^(I x)], x \[Element] Reals] > > I expect to get 'x'. > > Is there some way I can get this to simplify? >