Re: InequalitySolve
- To: mathgroup at smc.vnet.net
- Subject: [mg37825] Re: [mg37767] InequalitySolve
- From: Andrzej Kozlowski <andrzej at tuins.ac.jp>
- Date: Thu, 14 Nov 2002 06:11:30 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
This seems to be a bug in InequalitySolve. However, there is no bug in
In[1]:=
N[Experimental`CylindricalAlgebraicDecomposition[x^5-x^3-1==0&&0<x<2,x]]
Out[1]=
x==1.23651
On Tuesday, November 12, 2002, at 05:13 PM, PSi wrote:
> In[1]:= << Algebra`InequalitySolve`
>
> Example 1.
>
> In[2]:= N[InequalitySolve[x^5 - x^3 - 1 == 0 && 0 < x < 2, x] ]
> Out[2]:= x == 1.23651
>
> Example 2.
>
> In[3]:= NSolve[x^6 - x^3 - 1 == 0, x]
> Out[3]:= {{x -> -0.8518}, {x -> -0.586992 - 1.0167 I},
> {x -> -0.586992 + 1.0167 I }, {x -> 0.4259 - 0.73768 I},
> {x -> 0.4259 + 0.73768 I}, {x -> 1.17398}}
>
> In[4]:= N[InequalitySolve[x^6 - x^3 - 1 == 0 && 0 < x < 2, x] ]
>
> Of course the answer should be x == 1.17398 as in the first example.
> Instead of
> this, Mathematica 4.1 for Windows gives the following:
>
> Greater::"nord" : "Invalid comparison with
> (-1)^(2/3)(1/2-Sqrt[5]/2)^(1/3)
> attempted.
> Less::"nord" : "Invalid comparison with
> -2+(-1)^(2/3)(1/2-Sqrt[5]/2)^(1/3)
> attempted.
> Out[4]:= x>0.&&x<2.&&x==-0.8518+3.88578*10^-16 I || x == 1.17398
>
> Could anybody explain this?
> Thanks
> PSi
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Andrzej Kozlowski
Yokohama, Japan
http://www.mimuw.edu.pl/~akoz/
http://platon.c.u-tokyo.ac.jp/andrzej/