Let uppercase letters denote points in the plane
and lowercase letters denote the real numbers
assigned to the points.
Let A and B be arbitrary distinct points in the
plane. Construct the regular hexagon ABCDEF and
let G denote the intersection of rays CD and FE.
The points F and E are symmetrical to the
points C and D about the bisector of angle DGE.
Therefore, the triangles GDF and GEC have the same
incenter. thus,
(g+d+f)/3 = (g+e+c)/3
or
d+f = e+c.
Triangles ACE and BFD have the center of the hexagon as their
incenter. Thus,
(a+c+e)/3 = (b+f+d)/3
or
a = b.
Therefore, all points in the plane are assigned
the same real number.
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