Re: Absolute Value of Complex Numbers

*To*: mathgroup at smc.vnet.net*Subject*: [mg35202] Re: Absolute Value of Complex Numbers*From*: "Allan Hayes" <hay at haystack.demon.co.uk>*Date*: Tue, 2 Jul 2002 02:11:55 -0400 (EDT)*References*: <afp0oh$h08$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

"Kyle Davis" <kyledavis at nowhere.com> wrote in message news:afp0oh$h08$1 at smc.vnet.net... > Abs[2 Exp[3 * i]] > answer = 2 > > Abs[2 Exp[k * i]] > answer = 2 Exp[-Im[k]] > > Isn't the second answer supposed to be the same with the first one, regardless with the value of k? Only if k is real, but Mathematica allows for other values, for example Abs[2 Exp[I* I]] 2/E The general result is if k = x+I y then we get Abs[2 Exp[(x+I y)] = 2 Abs[ Exp[-y+ I x] ] = Abs[Exp[y] Exp[I x]] = Abs[Exp[-y]] = Exp[-y]] >How do I make the second calculation give me the right answer? Simplify[Abs[2 Exp[k * I]], Element[k, Reals]] 2 -- Allan --------------------- Allan Hayes Mathematica Training and Consulting Leicester UK www.haystack.demon.co.uk hay at haystack.demon.co.uk Voice: +44 (0)116 271 4198 Fax: +44 (0)870 164 0565 >