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Perfect Cuboid

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Brick

A perfect cuboid is a cuboid having integer side lengths, integer face diagonals

d_(ab)=sqrt(a^2+b^2)
(1)
d_(ac)=sqrt(a^2+c^2)
(2)
d_(bc)=sqrt(b^2+c^2),
(3)

and an integer space diagonal

d_(abc)=sqrt(a^2+b^2+c^2).
(4)

The problem of finding such a cuboid is also called the brick problem, diagonals problem, perfect box problem, perfect cuboid problem, or rational cuboid problem.

No perfect cuboids are known despite an exhaustive search for all "odd sides" up to 10^(10) (Butler, pers. comm., Dec. 23, 2004).

Solving the perfect cuboid problem is equivalent to solving the Diophantine equations

A^2+B^2=C^2
(5)
A^2+D^2=E^2
(6)
B^2+D^2=F^2
(7)
B^2+E^2=G^2.
(8)

A solution with integer space diagonal and two out of three face diagonals is a=672, b=153, and c=104, giving d_(ab)=3sqrt(52777), d_(ac)=680, d_(bc)=185, and d_(abc)=697, which was known to Euler. A solution giving integer space and face diagonals with only a single nonintegral polyhedron edge is a=18720, b=sqrt(211773121), and c=7800, giving d_(ab)=23711, d_(ac)=20280, d_(bc)=16511, and d_(abc)=24961.

See also

Cuboid, Diophantine Equation, Euler Brick, Face Diagonal, Heronian Tetrahedron, Heronian Triangle, Integer Triangle, Space Diagonal

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References

Butler, B. "Durango Bill's The 'Integer Brick' Problem (The Euler Brick Problem)." http://www.durangobill.com/IntegerBrick.html.Guy, R. K. "Is There a Perfect Cuboid? Four Squares whose Sums in Pairs are Square. Four Squares whose Differences are Square." §D18 in Unsolved Problems in Number Theory, 2nd ed. New York: Springer-Verlag, pp. 173-181, 1994.

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Perfect Cuboid

Cite this as:

Weisstein, Eric W. "Perfect Cuboid." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/PerfectCuboid.html

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