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Re: Absolute value

• To: mathgroup at smc.vnet.net
• Subject: [mg110617] Re: Absolute value
• From: DC <b.gatessucks at gmail.com>
• Date: Mon, 28 Jun 2010 02:30:07 -0400 (EDT)
• References: <i073n4$kk1$1@smc.vnet.net>

Try ComplexExpand as in :

In[9]:= Simplify[
   ComplexExpand[Abs[Exp[I phi1] + Exp[I*phi2]]]] // TrigReduce

Out[9]= Sqrt[2] Sqrt[1 + Cos[phi1 - phi2]]

-Francesco

On 06/27/2010 09:56 AM, Marco Masi wrote:
> I would like to calculate the absolute value of complex quantities. For example Abs[Exp[I phi1]+Exp[I*phi2]], which sould give 2 (1+cos(phi1-phi2)). However it does not work. I tried to use real numbers as assumtion, but it always answers "Abs[Exp[I phi1]+Exp[I*phi2]]". What am I doing wrong?
>
> Regards, Mark.
>