Browsing by Author "Tadeu, Pedro"
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- Conjugacy and geometry I : foot of the perpendicular, distance and gram determinantPublication . Costa, Cecília; Martins, Fernando M. L.; Serôdio, Rogério; Tadeu, Pedro; Vincente, M. A. Facas; Vitória, JoséIn this note on space geometry, the Gram determinant is used for expressing distances, vectors whose magnitude equals those distances and best approximation points. Three cases are considered: distances from a point to a line and to a plane and distances between two skew lines. (Symbolic) determinants occur in the expressions of the feet of perpendiculars and in the representation of the vectors materializing the distances. Because best approximation problems often require the use of subspaces, in order to solve the general cases of the proposed problems, we make extensive use of the conjugacy principle much present in Mathematics. The main purpose of this paper, focused on the resolution of distance problems in tridimensional geometry, is to provide the acquisition of spatial abilities through the proposed constructive approach. The obtained results, which could be a starting point and give clues for solving more advanced geometry problems, are applicable in several fields of practical sciences, such as the Coordinate Metrology, for instance. Moreover, this paper may be a window for coming across with a diversity of scalar products.
- Conjugacy and geometry II : moore-penrose inverse and feet of the perpendicularsPublication . Costa, C.; Martins, Fernando M. L.; Serôdio, Rogério; Tadeu, Pedro; Vincente, M. A. Facas; Vitória, JoséIn this paper on space geometry, generalized inverses are used in the study of distances. Three cases are considered: distance from a point to a plane, distance from a point to a line and distance between two skew lines. Moore-Penrose inverses occur in the expressions of the feet of the perpendiculars and in the representation of the vectors materializing the distances. The results of this kind of problems fit in the cadre of approximation theory and, because best approximation problems often require the projection of the origin onto linear varieties, in order to solve the proposed problems, we make extensive use of the conjugacy principle, much present in Mathematics. The obtained results are not only useful for undergraduate Science and Engineering students but are also applicable in very practical sciences and techniques, notably on Coordinate Metrology, Photogrammetry, etc. Moreover, this paper could pave the way for more generalized problems demanding more sophisticated approaches.
- Distance between linear varieties in ℝn. application of an (in)equality by (fan-todd) beesackPublication . Vicente, M. A. Facas; Vitória, José; M. L. Martins, Fernando; Costa, C.; Tadeu, PedroThe closest point of a linear variety to an external point is found by using the equality case of an Ostrowski’s type inequality. This point is given in a closed form as the quotient of a formal and a scalar Gram determinant. Then the best approximation pair of points onto two linear varieties is obtained, besides its characterization.