Re: Taking the Arg of a complex number

• To: undisclosed-recipients:;
• Subject: [mg122106] Re: Taking the Arg of a complex number
• From: Alexei Boulbitch <Alexei.Boulbitch at iee.lu>
• Date: Fri, 14 Oct 2011 05:53:47 -0400 (EDT)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com

```Here ComplexExpand should help. Try this:

(* This is youe expression*)

x=Exp[I*\[CurlyPhi]]

E^(I \[CurlyPhi])

(* This is the answer *)

y=ComplexExpand[Arg@x]

ArcTan[Cos[\[CurlyPhi]],Sin[\[CurlyPhi]]]

(*  Let us check, if it returns an expected result *)

y/.\[CurlyPhi]->\[Pi]/4

\[Pi]/4

Have fun.

Would appreciate any help here, endless Googling has not revealed the answer to me:

If I define a complex number symbolically, such as x = A Exp[I phi], why does Arg[x] never return the answer I expect, phi? Using Refine with the as sumptions phi is real and between 0 and 2 pi, and that A is greater than 0 doesn't seem to help. All I get is Arg[Exp[I phi]]

Alexei BOULBITCH, Dr., habil.

IEE S.A.

ZAE Weiergewan,

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mobile phone:  +49 151 52 40 66 44

e-mail: alexei.boulbitch at iee.lu<mailto:alexei.boulbitch at iee.lu>

```

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