Re: symbolic complex expressions

• To: mathgroup at smc.vnet.net
• Subject: [mg53677] Re: symbolic complex expressions
• From: "Scout" <user at domain.com>
• Date: Sat, 22 Jan 2005 03:52:15 -0500 (EST)
• References: <csqqmb\$1lk\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

Hi,

"Frank"
> Hi,
>
> I've 2 question with mathematica using symbolic complex expressions.
>
> - Is there a possibility to make from i.e. |x + I y| -> sprt(x^2+y^2)
> if x and y are Real. Abs[] doesn't work?
>

In[]:=
ComplexExpand[Abs[x + I y], TargetFunctions->{Re,Im}]

This forces Math. to assume both x and y are real.

>
> - You've a fraction like this x/(x + I y) and you want to eliminate
> the complex expression in the denominator.
> i.e. doing something like this: x/(x + Iy)*(x - I y)/(x - I y) -> (x^2
> - I x y)/(x^2+y^2)
>
As above...

In[]:=
ComplexExpand[x/(x + I y), TargetFunctions->{Re,Im}]

Bye,
~Scout~

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