On Best Approximation and Best Coapproximation

Tulsi Dass Narang, Sahil Gupta

Abstract

In this paper, the concept of best coapproximation is employed to prove various characterizations of proximinal, coproximinal, Chebyshev and co-Chebyshev subspaces. The continuity properties of metric projection, metric coprojection and related maps have also been discussed. The underlying spaces are normed linear spaces and metric linear spaces.