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RE: Complex Numbers

• To: mathgroup at smc.vnet.net
• Subject: [mg47439] RE: [mg47425] Complex Numbers
• From: "David Park" <djmp at earthlink.net>
• Date: Mon, 12 Apr 2004 03:44:53 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

Alejandro,

Give ComplexExpand a chance to work on the entire expression.

Re[Exp[a I] Exp[b I]] // ComplexExpand
Cos[a + b]

David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/



From: Alejandro Vizcarra [mailto:gebankos at prodigy.net.mx]
To: mathgroup at smc.vnet.net

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