Re: Re: Imaginary ...
- Subject: [mg2529] Re: [mg2490] Re: [mg2430] Imaginary ...
- From: hay at haystack.demon.co.uk (Allan Hayes)
- Date: Thu, 16 Nov 1995 06:46:17 GMT
- Approved: usenet@wri.com
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- Newsgroups: wri.mathgroup
- Organization: Wolfram Research, Inc.
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Jesus ROJO <jesroj at wmatem.eis.uva.es>
in [mg2490] Re: [mg2430] Imaginary ...
warns about
f:=a+I b
Sqrt[f*Conjugate[f]]//ComplexExpand
Sqrt[(a+I b) Conjugate[a+I b]]
I have recently been dealing with this laziness of ComplexExpand on
some quite large expressions.
The following might be of interest
ComplexExpand[Sqrt[f*Conjugate[f]],TargetFunctions ->{Re,Im}]
Sqrt[(a - I b) (a + I b)]
Repeat:
ComplexExpand[%,TargetFunctions ->{Re,Im}]
2 2
Sqrt[a + b ]
So I used FixedPoint to automate the process
FixedPoint[
ComplexExpand[#, TargetFunctions ->{Re,Im}]&,
Sqrt[f Conjugate[f]]
]
2 2
Sqrt[a + b ]
Allan Hayes
hay at haystack.demon.co.uk