MathDB
2 lines intersect inside a regular triangular pyramid

Source: IV Soros Olympiad 1997-98 R3 11.11 https://artofproblemsolving.com/community/c2416727_soros_olympiad_in_mathematics

June 2, 2024
pyramidgeometry3D geometry

Problem Statement

An arbitrary point MM is taken on the basis of a regular triangular pyramid. Let KK, LL, NN be the projections of MM onto the lateral faces of this pyramid, and PP be the intersection point of the medians of the triangle KLNKLN. Prove that the straight line passing through the points MM andP P intersects the height of the pyramid (or its extension). Let us denote this intersection point by EE. Find MP:PEMP: PE if the dihedral angles at the base of the pyramid are equal to aa.