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Re: Is this a bug?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg90842] Re: Is this a bug?
  • From: Peter Breitfeld <phbrf at t-online.de>
  • Date: Sat, 26 Jul 2008 04:20:16 -0400 (EDT)
  • References: <g6c982$brv$1@smc.vnet.net>

mailcwc at gmail.com schrieb:
> I tried to solve the following equation with mathematica 6.03
>
> Solve[{Abs[X+Y I]==5,X==3},{X,Y}]
>
> and got the answer
>
> {{X -> 3, Y -> -2 I}, {X -> 3, Y -> 8 I}}
>
> Am I  suppose to get {{X -> 3, Y -> 4 I}, {X -> 3, Y -> -4 I}} ?

No, you suppose to get {{X->3, Y->4},{X->3, Y->-4}} (without I),
that's what I would expect too.

The solutions Mathematica gives are correct -- just plug in. But you are
right, they are not what one would expect. 

This will give you the expected result:

Solve[{ComplexExpand[Abs[x+I y]]==5,x==3},{x,y}]

Gruss Peter
-- 
==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==
Peter Breitfeld, Bad Saulgau, Germany -- http://www.pBreitfeld.de


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