  Using approximate symmetry methods for differential equations we have
investigated the exact and approximate symmetries of a Lagrangian for the
geodesic equations in the Kerr spacetime. Taking Minkowski spacetime as the
exact case, it is shown that the symmetry algebra of the Lagrangian is 17
dimensional. This algebra is related to the 15 dimensional Lie algebra of
conformal isometries of Minkowski spacetime. First introducing spin angular
momentum per unit mass as a small parameter we consider first-order approximate
symmetries of the Kerr metric as a first perturbation of the Schwarzschild
metric. We then consider the second-order approximate symmetries of the Kerr
metric as a second perturbation of the Minkowski metric. The approximate
symmetries are recovered for these spacetimes and there are no non-trivial
approximate symmetries. A rescaling of the arc length parameter for consistency
of the trivial second-order approximate symmetries of the geodesic equations
indicates that the energy in the charged-Kerr metric has to be rescaled and the
rescaling factor is $r$-dependent. This rescaling factor is compared with that
for the Reissner-Nordstr\"{o}m metric.
