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Re: Complex Numbers

• To: mathgroup at smc.vnet.net
• Subject: [mg47435] Re: Complex Numbers
• From: bobhanlon at aol.com (Bob Hanlon)
• Date: Mon, 12 Apr 2004 03:44:50 -0400 (EDT)
• References: <c5b0tc$7lc$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

Simplify[Re[Exp[a I] Exp[b I]], 
  Im[a]==0 && Im[b]==0]

Cos[a + b]

Also look at the standard add-on package Algebra`ReIm`


Bob Hanlon

In article <c5b0tc$7lc$1 at smc.vnet.net>, Alejandro Vizcarra
<gebankos at prodigy.net.mx> wrote:

<< 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]