Two tetrahedra are called orthologic if the lines through vertices of one and
perpendicular to corresponding faces of the other are intersecting. This is
equivalent to the orthogonality of non-corresponding edges. We prove that the
additional assumption of intersecting non-corresponding edges (``orthosecting
tetrahedra'') implies that the six intersection points lie on a sphere. To a
given tetrahedron there exists generally a one-parametric family of
orthosecting tetrahedra.
Two tetrahedra are called orthologic if the lines through vertices of one and
perpendicular to corresponding faces of the other are intersecting. This is
equivalent to the orthogonality of non-corresponding edges. We prove that the
additional assumption of intersecting non-corresponding edges (``orthosecting
tetrahedra'') implies that the six intersection points lie on a sphere. To a
given tetrahedron there exists generally a one-parametric family of
orthosecting tetrahedra.