# Three Planes in a Trihedron

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Start with a trihedron with apex and edges , , . Extend the edges by a factor to a trihedron , , . Then the planes , and are concurrent. The common point is shown in red.

Contributed by: Izidor Hafner (May 2017)

Open content licensed under CC BY-NC-SA

## Snapshots

## Details

This problem was posed in [1, p. 220].

Reference

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

## Permanent Citation

"Three Planes in a Trihedron"

http://demonstrations.wolfram.com/ThreePlanesInATrihedron/

Wolfram Demonstrations Project

Published: May 5 2017