MathDB

Let

ABCA'B'C'

be a centrosymmetric octahedron (vertices

A

and

A'

B

and

B'

C

and

C'

are opposite) such that the sums of four planar angles equal

240^o

for each vertex. The Torricelli points

T_1

and

T_2

of triangles

ABC

and

A'BC

are marked. Prove that the distances from

T_1

and

T_2

BC

are equal.

10.8