  We present a construction of the basic operators of stochastic analysis
(gradient and divergence) for a class of discrete-time normal martingales
called obtuse random walks. The approach is based on the chaos representation
property and discrete multiple stochastic integrals. We show that these
operators satisfy similar identities as in the case of the Bernoulli randoms
walks. We prove a Clark-Ocone-type predictable representation formula, obtain
two covariance identities and derive a deviation inequality. We close the
exposition by an application to option hedging in discrete time.
