  In this article, we investigate the possibility of approximating the physical
inner product of constrained quantum theories. In particular, we calculate the
physical inner product of a simple cosmological model in two ways: Firstly, we
compute it analytically via a trick, secondly, we use the complexifier coherent
states to approximate the physical inner product defined by the master
constraint of the system. We will find that the approximation is able to
recover the analytic solution of the problem, which solidifies hopes that
coherent states will help to approximate solutions of more complicated
theories, like loop quantum gravity.
