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Inequality in a tetrahedron

Source: Moldova NMO 2002 grade 11 problem nr.8

November 3, 2008
inequalitiesgeometry3D geometrytetrahedroncircumcircle

Problem Statement

The circumradius of a tetrahedron ABCD ABCD is R R, and the lenghts of the segments connecting the vertices A,B,C,D A,B,C,D with the centroids of the opposite faces are equal to ma,mb,mc m_a,m_b,m_c and md m_d, respectively. Prove that: m_a\plus{}m_b\plus{}m_c\plus{}m_d\leq \dfrac{16}{3}R