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Classical solid geo from Romania

Source: Romanian NMO 2021 grade 8 P1

April 15, 2023
solid geometrygeometry

Problem Statement

In the cuboid ABCDABCDABCDA'B'C'D' with AB=aAB=a, AD=bAD=b and AA=cAA'=c such that a>b>c>0a>b>c>0, the points EE and FF are the orthogonal projections of AA on the lines ADA'D and ABA'B, respectively, and the points MM and NN are the orthogonal projections of CC on the lines CDC'D and CBC'B, respectively. Let DFBE={G}DF\cap BE=\{G\} and DNBM={P}DN\cap BM=\{P\}.
[*] Show that (AAG)(CCP)(A'AG)\parallel (C'CP) and determine the distance between these two planes; [*] Show that GP(ABC)GP\parallel (ABC) and determine the distance between the line GPGP and the plane (ABC)(ABC).
Petre Simion, Nicolae Victor Ioan