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MathGroup Archive 1993

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Is this a bug in AbsArg?

  • To: mathgroup at yoda.physics.unc.edu
  • Subject: Is this a bug in AbsArg?
  • From: mek at guinan.psu.edu (Mark E. Kotanchek)
  • Date: Tue, 24 Aug 93 22:02:50 -0400

Hi folks,

I was browsing ftp.wri.com and came across Declare.m and AbsArg.m which would  
appear to help to simplify some equations. However, if I use AbsArg I seem to  
get some strange and incorrect results. If I execute the following (running Mma  
2.1 on my NeXTstation), we get the results:

   Im[phi] ^= 0   =====> 0
                          I phi
   z=Exp[I phi]   =====> E  

                              I phi
   Arg[z]         =====> Arg[E     ]
   Arg[phi]       =====> Arg[phi]

If I then load the AbsArg package, my results change to 


   Im[phi] ^= 0  ======> 0
                          I phi   

   z=Exp[I phi]  ======> E
   Arg[z]        ======> 0
   Arg[phi]      ======> Arg[phi]

I was sort of expecting that Arg[z] would give me the phasor angle, phi. I  
think the resulting answer of zero is dangerously incorrect. Am I correct in  
this assessment?

Will Mathematica ever understand anything other than real algebra? (in a  
mainstream and supported fashion.)

Mark.
---
Mark Kotanchek
Guidance & Control Dept - 363 ASB
Applied Research Lab/Penn State
P.O. Box 30
State College, PA 16804

e-mail:	mek at guinan.psu.edu (NeXTmail)
TEL:	(814)863-0682
FAX:	(814)863-7843





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