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