Convex disks can cover their shadow
The authors give a short proof of the fact that given any 2-dimensional convex disk C in \({\mathbb{R}}^ 3\) and an orthogonal projection \(C'\) of C on a plane, then there is a congruent copy of C which contains \(C'\). [See \textit{M. D. Kovalev}, Ukr. Geom. Sb. 27, 57-68 (1984; Zbl 0551.52003) and \textit{H. E. Debrunner} and \textit{P. Mani-Levitska}, Discrete Comput. Geom. 1, 45-58 (1986; Zbl 0593.52002)].
scientific article; zbMATH DE number 4171843