On an Expression for the Midpoint and the Radius of the Product of Two Intervals

The paper deals with expressions for the midpoint and the radius of the product of two intervals. Based on these expressions two applications are considered: One leads to an explicit representation of the fixed point of the function [A][x]+ [b] if zero is contained in the interval vector [b] but not in the interior of the entries of the interval matrix [A]. The second application proves the semi–convergence of an interval matrix [A] under certain assumptions which are not studied up to now.