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Re: FindInstance puzzler

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  • Subject: [mg83654] Re: FindInstance puzzler
  • From: Tom Burton <news at>
  • Date: Tue, 27 Nov 2007 06:15:54 -0500 (EST)

A diagnosis seems easy enough, but so far a cure eludes me. Observe  
that your conditions contain the radical Sqrt[z1^2+4z2]. Your  
invocation of FindInstance asks it to assume that, not only the  
variables but also all function values are real, in particular Sqrt,  
implying that z1^2+4z2>0. Indeed, all points found satisfy this  
condition. No puzzler here. Unfortunately, when I try the suggested  
variation to relax this assumption,


the kernel goes out to lunch.  I hope someone has a better idea.


When responding, please replace news with my first initial and full  
last name, as one word.

Tom Burton

> ...
> RegionPlot[conds, {z1, -.75, 2.25}, {z2, -1.25, 1.25}, PlotPoints - 
> > 90,
>  Epilog ->  Point[{z1, z2} /. FindInstance[conds, {z1, z2}, Reals,  
> 10^3]]]
> ...

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