  We present a method to determine the angular momentum of a black hole, based
on observations of the trajectories of the bodies in the Kerr space-time. We
use the Hamilton equations to describe the dynamics of a particle and present
results for equatorial trajectories, obtaining an algebraic equation for the
magnitude of the black hole's angular momentum. We tailor a numerical code to
solve the dynamical equations and use it to generate synthetic data. We apply
the method in some representative examples, obtaining the parameters of the
trajectories as well as the black hole's angular momentum in good agreement
with the input data.

General Relativity and Quantum Cosmology;Astrophysics of Galaxies