Achill <ach### [at] matumde> wrote in news:3EA### [at] matumde:

> 
>>>Mathematically, the (vector) sum A+B of two sets A and B is defined
>>>as the set of all points x=a+b with a in A and b in B.
>>>A+B = { x : x=a+b, a in A and b in B }.

...

> A concrete example would be the sum of the tetrahedron T with vertices
> <0,0,0>, <1,0,0>, <0,1,0> and <0,0,1> with "its negative" -T with 
> vertices <0,0,0>, <-1,0,0>, <0,-1,0> and <0,0,-1>.
> The outcome is a polyhedron (polytope) with vertices
> <-1, 0, 0>, <0, -1, 0>, <0, 0, -1>, <1, 0, 0>, <1, -1, 0>, <1, 0, -1>,
> <0, 1, 0>, <-1, 1, 0>, <0, 1, -1>, <0, 0, 1>, <-1, 0, 1>, <0, -1, 1>.
...

Why isn't <0, 0, 0> in the outcome list ?


Tor Olav

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