Assertion: tetrahedron | /r/HasProperty | orthocentric
Facets:
Source sentences:
text: A tetrahedron is orthocentric if and only if its circumscribed parallelepiped is a rhombohedron.
text: If four faces of a parallelepiped are rhombi, then all edges have equal lengths and all six faces are rhombi; it follows that if two pairs of opposite edges in a tetrahedron are perpendicular, then so is the third pair, and the tetrahedron is orthocentric.
text: In fact, it is enough for only two pairs of opposite edges to satisfy this condition for the tetrahedron to be orthocentric.
text: Another necessary and sufficient condition for a tetrahedron to be orthocentric is that its three bimedians have equal length.