On 3/30/07, Marshall Hampton <[EMAIL PROTECTED]> wrote:
>
> Why do you need that extra minus? I believe my original function was
> correct - perhaps you are thinking of the expansion in 2x2 minors? Or
Ooops, you're right. I wasn't thinking. (Or if I was, it was of the
minor expansion).
You're version puts the minus sign in automatically.
> am I missing something?
>
> -Marshall
>
> On Mar 30, 12:00 pm, "David Joyner" <[EMAIL PROTECTED]> wrote:
> > On 3/30/07, Marshall Hampton <[EMAIL PROTECTED]> wrote:
> >
> >
> >
> >
> >
> > > Here's a function definition to avoid using maxima:
> >
> > > def cross_product(vec1,vec2):
> > > r'''
> > > This returns the cross product of 2 three-dimensional vectors.
> >
> > > INPUT:
> > > vec1 - the first 3D vector in the cross product
> > > vec2 - the second 3D vector in the cross product
> >
> > > OUTPUT:
> > > A 3D vector
> >
> > > EXAMPLES:
> > > basic usage:
> > > sage: cross([1,2,3],[2,3,4])
> >
> > sage: cross_product([1,2,3],[2,3,4])
> >
> > > [-1, 2, -1]
> >
> > > NOTES:
> > > This is a crude first attempt.
> > > '''
> > > x,y,z = QQ['x,y,z'].gens()
> > > mat = matrix([[x,y,z],vec1,vec2])
> > > d = det(mat)
> > > return [d(1,0,0),d(0,1,0),d(0,0,1)]
> >
> > return [d(1,0,0),-d(0,1,0),d(0,0,1)]
> >
> >
> >
> > > On Mar 30, 11:33 am, "Marshall Hampton" <[EMAIL PROTECTED]> wrote:
> > > > Hi,
> >
> > > > I am not an expert on SAGE but I was curious about your question and
> > > > tried to find an answer. I am curious about better ways to do this.
> >
> > > > Anyway, the first thing I found that works is to use maxima's vect
> > > > package. For some reason it uses '~' as the cross-product operator.
> > > > As an example:
> >
> > > > sage: maxima.load('vect')
> > > > ?\/Users\/mh\/sage\ - 2\.1\.0\.1\/local\/share\/maxima\/5\.11\.0\/share
> > > > \/vector\/vect\.mac
> > > > sage: maxima('express([1,2,3]~[2,3,4])')
> > > > [ - 1,2, - 1]
> >
> > > > At some point it would be nice to have a native SAGE way to do this
> > > > and other differential form computations; given the developer's
> > > > interest in modular forms this probably wouldn't be extremely
> > > > difficult.
> >
> > > > -M.Hampton
> >
> > > > On Mar 30, 4:58 am, "microdev" <[EMAIL PROTECTED]> wrote:
> >
> > > > > hello,
> >
> > > > > I have tried the dot product :
> >
> > > > > v = (1,2,3)
> > > > > v1 = (2,4,6)
> > > > > v.dot_product(v1) -> ok
> >
> > > > > and for the cross product?
> >
> > > > > thank you for help..
> >
> > > > > Felix
>
>
> >
>
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to [email protected]
To unsubscribe from this group, send email to [EMAIL PROTECTED]
For more options, visit this group at
http://groups.google.com/group/sage-support
URLs: http://sage.math.washington.edu/sage/ and http://sage.scipy.org/sage/
-~----------~----~----~----~------~----~------~--~---
