IMO 1972 LL BUL5

Given a pyramid whose base is an n-gon inscribable in a circle,

imolonglistmathematicsolympiad

IMO 1972 LL BUL5

Origin: BUL

Problem

Given a pyramid whose base is an n-gon inscribable in a circle, let H be the projection of the top vertex of the pyramid to its base. Prove that the projections of H to the lateral edges of the pyramid lie on a circle.