Journal Home Page Cumulative Index List of all Volumes Complete Contentsof this Volume Previous Article Journal for Geometry and Graphics 10 (2006), No. 2, 155--160Copyright Heldermann Verlag 2006 On a Problem of Elementary Differential Geometry and the Number of its Solutions Johannes Wallner Institute of Geometry, Technical University, Kopernikusgasse 24, 8010 Graz, Austria j.wallner@tugraz.at [Abstract-pdf] If $M$ and $N$ are submanifolds of ${\mathbb R}^k$, and $a$, $b$ are points in ${\mathbb R}^k$, we may ask for points $x\in M$ and $y\in N$ such that the vector $\vec{ax}$ is orthogonal to $y$'s tangent space, and vice versa for $\vec{by}$ and $x$'s tangent space. If $M,N$ are compact, critical point theory is employed to give lower bounds for the number of such related pairs of points. Interestingly, we also employ the curvature theory of hypersurfaces in a pseudo-Euclidean space, where curvatures are not considered as real numbers, but as linear forms in the normal space of a point. Keywords: Curves and surfaces, critical points, pseudo-euclidean distance. MSC: 53A05; 53A30, 57D70 [ Fulltext-pdf  (124  KB)] for subscribers only.