Let
be three rays, and
a point inside the trihedron
. Consider all planes passing through
and cutting
at points
, respectively. How is the plane to be placed in order to yield a tetrahedron
with minimal perimeter ?
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Let $Ox, Oy, Oz$ be three rays, and $G$ a point inside the trihedron $Oxyz$. Consider all planes passing through $G$ and cutting $Ox, Oy, Oz$ at points $A,B,C$, respectively. How is the plane to be placed in order to yield a tetrahedron $OABC$ with minimal perimeter ?