Dan Connelly wrote:
> 
> Ron Parker wrote:
> > Whoops, lathe and sor too.  What about TTFs that are created from the
> > lower left corner?
> 
> ... and superelipsoids, of course, which raises the question of why
> superellipsoids are symmetric in x and y while almost everything else
> is symmetric in x and z.
> 
> It's clear the only consistency in POV is there is no consistency.
> It's like UNIX and basically every other piece-meal project.... the
> inconsistency just adds to its attractive character.
> 
> > what's the cross-product of two 4-d vectors?
> 
> Good question!  I expect it would take 3 vectors to yield a cross
> product :
> 
> y_i = a_j b_k c_l e_ijkl
> 
> (a, b, c are 4-vectors, e is a matrix)
> 
> where e_ijkl = 0 for and two elements of {i,j,k,l} equal,
> +1, or -1 in other cases.
> 
> But cross products of 3-d vectors don't yield vectors, but pseudovectors,
> as the result depends on handedness.  Either this or my physics background
> is too faded for such details.

The cross product of two 3d vectors certainly does yield another vector.
If it didn't, half of my code wouldn't work!

Regards,
John

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