Re: Getting Symbolic Real and Imag Parts? (Once Again)

• To: mathgroup at smc.vnet.net
• Subject: [mg33462] Re: Getting Symbolic Real and Imag Parts? (Once Again)
• From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
• Date: Fri, 22 Mar 2002 04:06:39 -0500 (EST)
• Organization: Universitaet Leipzig
• References: <a7cs6t\$hv8\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

Hi

as you do it wit paper and pencil

SymbolicRe[z_] := (z + (z /. Complex[a_, b_] :> Complex[a, -b]))/2
SymbolicIm[z_] := (z - (z /. Complex[a_, b_] :> Complex[a, -b]))/(2 I)

Regards
Jens

aes wrote:
>
> OK,  so you can use ComplexExpand expand to find the symbolic real and imag
> parts of an expression -- e.g. the input
>
>       zComplex = ComplexExpand[ Sin[a+I b], TargetFunctions->{Re,Im}]
>
> gives as output
>
>       Cosh[b] Sin[a] + I Cos[a] Sinh[b]
>
> as desired.  But now, how do I get Mathematica to peel out the symbolically real and
> imaginary parts of this? -- that is, what inputs
>
>       zR = ???
>
>       zI = ???
>
> will give as outputs
>
>       Cosh[b] Sin[a]
>
> and
>
>       Cos[a] Sinh[b]
>
> (Maybe an example in the ComplexExpand Help file would be helpful?)

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