  Angular deviations and lateral displacements are optical effects widely
investigated in literature. In this paper, by using the Taylor expansion of the
Fresnel coefficients, we obtain an analytic expression for the beam reflected
by and (upper) transmitted through a dielectric prism. These analytical
approximations lead to a cubic equation which allows to determine the angular
deviations of the optical beams. Near the Brewster angles, under specific
conditions, we obtain a universal formulation for the cubic equation. Its
explicit solution determines the peak position of the reflected and (upper)
transmitted beams. The universal solution could be of great utility in future
experimental implementations. The analytic results show an excellent agreement
with the numerical calculation and the analytic expressions given for the
reflected and (upper) transmitted beams should play an important role in the
weak measurements analysis.
