Re: FindInstance puzzler

*To*: mathgroup at smc.vnet.net*Subject*: [mg83696] Re: [mg83633] FindInstance puzzler*From*: Andrzej Kozlowski <akoz at mimuw.edu.pl>*Date*: Wed, 28 Nov 2007 05:41:04 -0500 (EST)*References*: <200711260849.DAA29897@smc.vnet.net> <55F7C11F-CAB8-47B4-AE40-DA470C74C8C1@mimuw.edu.pl> <474AF639.50705@wolfram.com> <52B4543A-8103-4C24-9786-8C554D247748@mimuw.edu.pl>

On 27 Nov 2007, at 17:05, Andrzej Kozlowski wrote: > Reduce[2*y*I*Sqrt[x] + 2*(y - I*Sqrt[x]) == 0, {x, y}, Reals] This should have been: In[17]:= Reduce[2*y*I*Sqrt[x] + 2*(y - y*I*Sqrt[x]) == 0, {x, y}, Reals] During evaluation of In[17]:= Reduce::nddc:The system 2 \[ImaginaryI] Sqrt[x] y+2 (y-\[ImaginaryI] Sqrt[x] y)\[LongEqual]0 contains a nonreal constant 2 \[ImaginaryI]. With the domain \ [DoubleStruckCapitalR] specified, all constants should be real. >> Out[17]= Reduce[2*I*Sqrt[x]*y + 2*(y - I*Sqrt[x]*y) == 0, {x, y}, Reals] but it other than that it does not change anything. Note that: Reduce[Simplify[2*y*I*Sqrt[x] + 2*(y - y*I*Sqrt[x]) == 0], {x, y}, Reals] y==0 What I really mean tto say is: wouldn't it be a litte better to first automatically apply Simplify in such situation to see if the I's could be got rid of? Andrzej Kozlowski

**References**:**FindInstance puzzler***From:*Mark Fisher <particlefilter@gmail.com>