RE: Real coefficients in complex numbers

• To: mathgroup at smc.vnet.net
• Subject: [mg15777] RE: [mg15734] Real coefficients in complex numbers
• From: "Ersek, Ted R" <ErsekTR at navair.navy.mil>
• Date: Sun, 7 Feb 1999 02:03:54 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

```Niels Langager Ellegaard  wrote:
_________________________

If you are calculations with complex numbers: a + I b How do you state
that a and b are real? For example I might want to calculate the real
part of

a + 1/(b + 1/(1/I c + d)) ; Where a,b,c,d are real

Can this be done in a nice way. (Yes, I do know how to do the
calculation by hand)

________________________

Use ComplexExpand.

In[1]:=
?ComplexExpand
"ComplexExpand[expr] expands expr assuming that all variables are real.
ComplexExpand[expr, {x1, x2, ... }] expands expr assuming that
variables matching any of the xi are complex."

In[2]:=
Re[a + 1/(b + 1/(1/I c + d))]//ComplexExpand

(* Output not shown *)

Regards,
Ted Ersek

```

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