# Sum of the Squares of the Sides of a Projected Regular Tetrahedron

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Let be a regular tetrahedron with side . Project orthogonally to a plane and let , , …, be the lengths of the projections of the six sides of in . This Demonstration shows that .

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Contributed by: Izidor Hafner (June 2017)

Open content licensed under CC BY-NC-SA

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## Details

This problem was posed in [1, pp. 20, 28].

Reference

[1] V. V. Prasolov and I. F. Sharygin, *Problems in Stereometry* (in Russian), Moscow: Nauka, 1989.

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