       Re: Is this a bug?

• To: mathgroup at smc.vnet.net
• Subject: [mg90845] Re: Is this a bug?
• From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
• Date: Sat, 26 Jul 2008 04:20:49 -0400 (EDT)
• Organization: The Open University, Milton Keynes, UK
• References: <g6c982\$brv\$1@smc.vnet.net>

```mailcwc at gmail.com wrote:

> I tried to solve the following equation with mathematica 6.03
>
> Solve[{Abs[X+Y I]==5,X==3},{X,Y}]
>
>
> {{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}} ?

generic solutions only. It discards solutions that are valid only when
the parameters satisfy special conditions. Reduce gives the complete set
of solutions." For instance,

In:=
eqns = {Abs[x + y*I] == 5, x == 3};
sols = Solve[eqns]
eqns /. sols
eqns /. {{x -> 3, y -> 4 I}, {x -> 3, y -> -4 I}}
Reduce[eqns]

Out= {{x -> 3, y -> -2 I}, {x -> 3, y -> 8 I}}

Out= {{True, True}, {True, True}}

Out= {{False, True}, {False, True}}

Out=
2
-2 <= Im[y] <= 8 && (Re[y] == -Sqrt[16 + 6 Im[y] - Im[y] ] ||

2
Re[y] == Sqrt[16 + 6 Im[y] - Im[y] ]) && x == 3

See

http://reference.wolfram.com/mathematica/ref/Solve.html

http://reference.wolfram.com/mathematica/ref/Reduce.html

Regards,
-- Jean-Marc

```

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