Option Pricing Formulas Under a Change on Numéraire

We present some formulations of the Cox-Ross-Rubinstein and Black-Scholes for- mulas for European options obtained through a suitable change of measure, which corresponds to a change of numeraire for the underlying price process. Among other consequences, a closed formula for the price of an European call option at each node of the multi-period binomial tree is achieved, too. Some of the results contained herein, though comparable with analogous ones appearing in [7] and [8], provide however a supplementary widening and deepening in view of useful applications in the more challenging framework of incomplete markets. This last issue, having the present paper as a preparatory material, will be treated extensively in a forthcoming paper.