2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/150274First, we consider a compact real-analytic irreducible subvariety $M$ in a sphere and its dual variety $M^\vee$. We explain that two matrices of the second fundamental forms for both varieties $M$ and $M^\vee$ can be regarded as the inverse matrices of each other. Also generalization in hyperbolic space is explained.LaTeX2e+AmsLaTeX. 3 pages. This manuscript was submitted to Proceedings of Symposium Real Analytic and Algebraic Singularities(IS(J held at Nagoya University in September - October, 1996. Adobe PDF version is available also at http://urabe-lab.math.metro-u.ac.jp/Algebraic Geometrytext