On Dec 8, 9:36 pm, robin hankin <hankin.ro...@gmail.com> wrote:
> hello
>
> I have been playing with assumptions(). I want to assume a>b
> but solve() gives me a solution which is not consistent with this:
>
> sage: var('a b')
> (a, b)
> sage: assume(a>b)
> sage: assumptions()
> [a > b]
> sage: solve([a+b==2,a-b==0],a,b)
> [[a == 1, b == 1]]
> sage:
>
> How come the solution (viz a=b=1) is not consistent with my assumption()?
>
> --
> Robin Hankin
> Uncertainty Analyst
> hankin.ro...@gmail.com
Sometimes one can use workarounds:
sage: var('a b')
(a, b)
sage: sol=solve([a+b==2,a-b==0],a,b)
sage: [s for s in sol if s[0].rhs()>s[1].rhs()]
[]
sage: sol=((x+1)*x*(x-1)==0).solve(x)
sage: [s for s in sol if s.rhs()>0]
[x == 1]
sage: var('x y')
sage: sol=solve([x^2-4*x+y^2==0,y^4==x^2],x,y)
sage: [s for s in sol if all([s[0].rhs()>0,s[1].rhs()>0])]
[[x == 3, y == sqrt(3)]]
--
To post to this group, send email to sage-support@googlegroups.com
To unsubscribe from this group, send email to
sage-support+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/sage-support
URL: http://www.sagemath.org
