Best Approximation in TVS

Document Type: Research articles


Faculty of Mathematics, Ayatollah Boroujerdi University, Boroujerd, Iran


In this paper  we give new
results on the best approximation  in the Hausdorff topological vector
space and  consider relationship  with orthogonality. Also we determined under  what
 conditions the map $P_{K,f}$ is upper semicontinous.