Cominimal Projections inln∞ Original Research Article

LetY⊂ln∞be a subspace of codimension two and let P(ln∞, Y) denote the set of all linear projections fromln∞ontoY. A complete characterization ofYfor which there existsPo∈P(ln∞, Y) such that ‖Id−Po‖=1 will be given. Also an estimate from below of the constantλI(Y, ln∞)=inf{‖Id−P‖: P∈P(ln∞, Y)}as well as the formulas for cominimal projections in some particular cases will be presented.