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MathGroup Archive 2004

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Re: Complex Numbers

  • To: mathgroup at smc.vnet.net
  • Subject: [mg47437] Re: [mg47425] Complex Numbers
  • From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
  • Date: Mon, 12 Apr 2004 03:44:51 -0400 (EDT)
  • References: <200404110844.EAA07722@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

On 11 Apr 2004, at 17:44, Alejandro Vizcarra wrote:

> Hi,:
>
> I always have problems when dealing with complex numbers.  How can i
> work with Mathematica in such a way that every expression will
> be considered real unless it is declared explicitly complex (like a = 
> 3 + 4 I ) ?
>
> For example if I type
>
> Re[ComplexExpand[ Exp[a I] Exp[b I]]]
>
> I get the answer
>
> -Im[Sin[ a+b]]+Re[Cos[a+b]]
>
> Instead of simply Cos[a+  b]
>
> Thnx!
>
>
> Alejandro Vizcarra
>
>

Not

Re[ComplexExpand[ Exp[a I] Exp[b I]]]


but


ComplexExpand[Re[Exp[a I] Exp[b I]]]

Cos[a+b]


Andrzej Kozlowski
Chiba, Japan
http://www.mimuw.edu.pl/~akoz/


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