Re: Assumptions in MuPAD
- From: Peter Pein <petsie@xxxxxxxxxx>
- Date: Sun, 24 Jul 2005 15:58:20 +0200
swagat schrieb:
> Hi all!
>
> I am still having problem with "assume" function.
>
> Lets say, i have real numbers a,b,c,d,e,f,g,h. I want to test following
> statement in MuPAD.
>
> if ad>=bc and eh>=fg, then ah+ed>=bg+cf
>
> I first use global assumption:
> assume(Type::Real)
>
>
> but the statement
>
> assume(a*d>b*c)
>
> gives me following error
>
> Error: at least one side must be an (indexed) identifier [assume]
>
> How can i make such assumptions?
>
> Please help.
>
> Thanks and Regards,
> swagat
>
Before you (and MuPAD) try too hard:
test = Implies[a*d >= b*c && e*h >= f*g &&
{a, b, c, d, e, f, g, h} \[Element] Reals,
a*h + e*d >= b*g + c*f]
FindInstance[ !test, {a, b, c, d, e, f, g, h}, 3]
Out[10]=
{{a->-112, b->0, c->-80, d->-19, e->0, f->68, g->0, h->105},
{a->0, b->459, c->0, d->-80, e->35, f->-(33/10), g->65, h->-(429/70)},
{a->97, b->-86, c->32, d->-(2752/97), e->-45, f->72, g->56, h->-149}}
or with the additional restriction a..h>0:
{{a->66, b->88, c->101, d->404/3, e->101, f->205, g->31, h->89},
{a->189, b->76, c->78, d->58, e->96, f->101/3, g->312, h->5806/53},
{a->252, b->53, c->24, d->106/21, e->39, f->77, g->15/7, h->249/37}}
--
Peter Pein
Berlin
.
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- Assumptions in MuPAD
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