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Re: Absolute Value of Complex Numbers

• To: mathgroup at smc.vnet.net
• Subject: [mg35201] Re: [mg35196] Absolute Value of Complex Numbers
• From: Andrzej Kozlowski <andrzej at tuins.ac.jp>
• Date: Tue, 2 Jul 2002 02:11:53 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

And how is Mathematica to know what k is? For example, it could be = I, 
which will give the answer 2/E and so on. Of course you meant k to be 
real but unfortunately Mathematica's mind reading technology is still in 
the development stage and won't be available before version 9.1. In the 
mean time you have to use:

In[3]:=
ComplexExpand[Abs[2 Exp[k*I]]]

Out[3]=
2

or

In[4]:=
Simplify[Abs[2 Exp[k*I]],Element[k,Reals]]

Out[4]=
2

which is really more than enough.


Andrzej Kozlowski
Toyama International University
JAPAN
http://platon.c.u-tokyo.ac.jp/andrzej/

On Monday, July 1, 2002, at 04:34  PM, Kyle Davis wrote:

> 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? How do I make the second calculation 
> give me
> the right answer?
>
>
>
>