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Problem with ComplexExpand[Abs[]]

• To: mathgroup at christensen.cybernetics.net
• Subject: [mg1807] Problem with ComplexExpand[Abs[]]
• From: Paul E Howland <PEHOWLAND at taz.dra.hmg.gb>
• Date: Thu, 17 Aug 1995 00:01:58 -0400

I'm posting this on behalf of a colleague of mine.

He is running into a problem where 

	ComplexExpand[Abs[a + I b + Sqrt[a + I b]]]

will not evaluate further.  What's going on?  Is there a way to expand 
Sqrt[a + I b] into something of the form (d + I e) which Abs can cope 
with, or has he hit against some fundamental problem with complex algebra 
which says there is no general solution to this problem?

Any help would be much appreciated.

Paul E Howland                         

Long Range Ground Radar Systems Section               tel. +44 (0)1684 895767
LSC2 Division, Room BY209                             fax. +44 (0)1684 896315
Defence Research Agency                           email: PEHOWLAND at DRA.HMG.GB 
Malvern, Worcs, WR14 3PS, UK.                      
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