Perfect Parallelepiped
A perfect parallelepiped is a parallelepiped with integer-length edges, face diagonals, and body diagonals, but not necessarily with all right angles; a perfect cuboid is a special case of a perfect parallelepiped. In 2009, a perfect parallelepiped was shown to exist, answering an open question of Richard Guy. Solutions with only a single oblique angle have been found.
Read more about this topic: Euler Brick
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