Re: Repost: Solve: same or new bug?
- To: mathgroup at smc.vnet.net
- Subject: [mg17668] Re: Repost: Solve: same or new bug?
- From: adam.smith at hillsdale.edu
- Date: Fri, 21 May 1999 23:58:53 -0400
- Organization: Deja.com - Share what you know. Learn what you don't.
- References: <7i37g1$bin@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
I tried the example you listed on my machine and got a slightly
different result. In particular it gave me a warning message about not
finding all solutions. This is no doubt because of the square root in
the definition of m.:
m:=Sqrt[1-a^2]
g:=(x*(a+y)-m*(a+y+e))^2+y^2*(a+y+e)^2-(a+y+e)^2
gx:=D[g,x]
gy:=D[g,y]
Solve[{g==0,gx==0,gy==0},{x,y}]
Solve::"svars":"Equations may not give solutions for all \"solve\"
variables."
{{x -> 0, y -> -a - e}, {y -> -a}}
What version of Mathematica are you using? I am running version 3.0.1
under Windows NT. Although Wolfram claims that the versions are system
independent, I have seen several cases where there are slight
differences between operating systems and even between 3.0.0 and 3.0.1.
Adam Smith
In article <7i37g1$bin at smc.vnet.net>,
Thomas Gawlick <Thomas.Gawlick at uni-vechta.de> wrote:
>
>
> In the following example Mathematica happens to find a "general
> solution'" that does not special to a solution for numerical
> specialization of the paramters a,e.
>
> m:=Sqrt[1-a^2]
> g:=(x*(a+y)-m*(a+y+e))^2+y^2*(a+y+e)^2-(a+y+e)^2
> gx:=D[g,x]
> gy:=D[g,y]
> Solve[{g==0,gx==0,gy==0},{x,y}]
> {{x -> 0, y -> -a - e},
> {x -> (a*(1 - a^2)^(1/2)*e)/(-1 + a^2), y -> -a},
> {x -> (a*(1 - a^2)^(1/2)*e)/(-1 + a^2), y -> -a}}
> % /. {a->.5,e->.1}
> {{x -> 0, y -> -0.6}, {x -> -0.057735, y -> -0.5},
>
> {x -> -0.057735, y -> -0.5}}
> a:=.5; e:=.1
> Solve[{g==0,gx==0,gy==0},{x,y}]
> {{x -> 0., y -> -0.6}}
>
> Is the reason for this that Mathematica checks numerical solutions
only?
>
> Another small question: How do you achieve to clear ALL variables?
>
> --
> Best regards
>
> Thomas Gawlick
> ---
> Dr.rer.nat. Thomas Gawlick
>
> Hochschulassistent fur Didaktik der Mathematik
>
> Hochschule Vechta, 49364 Vechta
>
>
--== Sent via Deja.com http://www.deja.com/ ==--
---Share what you know. Learn what you don't.---