[Date Index] [Thread Index] [Author Index]

Re: Taking the Arg of a complex number

• To: mathgroup at smc.vnet.net
• Subject: [mg122117] Re: Taking the Arg of a complex number
• From: "Dr. Wolfgang Hintze" <weh at snafu.de>
• Date: Sat, 15 Oct 2011 06:02:49 -0400 (EDT)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• References: <j73grj$fvk$1@smc.vnet.net>

Along the lines of Alexei

x = A*Exp[I*phi]
A*E^(I*phi)

(* the next step effectively removes A ; does not work with A < 0 *)
FullSimplify[Arg[x], A > 0]
Arg[E^(I*phi)]

(* now ComplexExpand dos the rest *)
y = ComplexExpand[%]
ArcTan[Cos[phi], Sin[phi]]

Wolfgang

------------

"Ben" <bjgear at googlemail.com> schrieb im Newsbeitrag 
news:j73grj$fvk$1 at smc.vnet.net...
> 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]]
>