Proposition: Prop. 11.28: Parallelepiped cut by Plane through Diagonals of Opposite Planes is Bisected
(Proposition 28 from Book 11 of Euclid's “Elements”)
If a parallelepipedal solid is cut by a plane (passing) through the diagonals of (a pair of) opposite planes then the solid will be cut in half by the plane.
* For let the parallelepipedal solid $AB$ have been cut by the plane $CDEF$ (passing) through the diagonals of the opposite planes $CF$ and $DE$.
* I say that the solid $AB$ will be cut in half by the plane $CDEF$.
Modern Formulation
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Table of Contents
Proofs: 1
Mentioned in:
Proofs: 1 2 3
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References
Adapted from (subject to copyright, with kind permission)
 Fitzpatrick, Richard: Euclid's "Elements of Geometry"
Adapted from CC BYSA 3.0 Sources:
 Prime.mover and others: "Pr∞fWiki", https://proofwiki.org/wiki/Main_Page, 2016