Path: csiph.com!usenet.pasdenom.info!news.albasani.net!eternal-september.org!feeder.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: Joe Riel <joer@san.rr.com>
Newsgroups: comp.soft-sys.math.maple
Subject: Re: Reducing or Simplifying sqrt(2)
Date: Sat, 31 May 2014 21:20:34 -0700
Organization: A noiseless patient Spider
Lines: 32
Message-ID: <877g512rcd.fsf@san.rr.com>
References: <EpudnVOxHL2hPRfOnZ2dnUVZ_vKdnZ2d@megapath.net>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Injection-Info: mx05.eternal-september.org; posting-host="15591ad2607da309a0d1a78a1d632bc7"; logging-data="28782"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1+4x2/s0Twa6Y3eT663Subh"
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.4 (gnu/linux)
Cancel-Lock: sha1:6o/duzHw8OVRRq9NRMkKZ9POfWs= sha1:sofLSzXa2iDgStJlweLKHlaLSGs=
Xref: csiph.com comp.soft-sys.math.maple:881

"Thomas D. Dean" <tomdean@speakeasy.org> writes:

> with(geometry);
> _EnvHorizontalName:=x;
> _EnvVerticalName:=y;
> point(P1,[1,1]); ## point on the directrix
> point(V1,[2,2]); ## vertex
> point(P2,[3,3]); ## focus
> ## since the vertex is at V1, and the line of symmetry passes through
> ## the vertex,
> line(L,[P1,V1]); ## line os symmetry
> detail(L);
> PerpendicularLine(Lp,P1,L); ## directrix
> detail(Lp);
> distance(P2,V1);
> parabola(P,['vertex'=V1,'focus'=P2]);
> detail(P);
> ## the equation has sqrt(2) in every term
> eq:=Equation(directrix(P)); ## get the equation of the directrix
> expand(eq*sqrt(2));    ## This is what I want

Hmm.  Not sure.  You could do

(**) eliminate([eq],[x,y]);
                                     [{x = -y + 2, y = y}, {}]

(**) (lhs-rhs)(op(remove(evalb,%[1])));
                                            -2 + x + y


-- 
Joe Riel