At a 3/2-cusp of a given plane curve γ(t), both of the Euclidean curvature κg and the affine curvature κA diverge. In this paper, we show that each of ∣sg∣κg
Nearby in the stack
and
(sA)2κA
(called the Euclidean and affine normalized curvature, respectively) at a 3/2-cusp is a smooth function of the variable
t
, where
sg
(resp.
sA
) is the Euclidean (resp. affine) arclength parameter of the curve corresponding to the 3/2-cusp
sg=0
(resp.
sA=0
). Moreover, we give a characterization of the behaviour of the curvature functions
κg
and
κA
at 3/2-cusps. On the other hand, inflection points are also singular points of curves in affine geometry. We give a similar characterization of affine curvature functions near generic inflection points. As an application, new affine invariants of 3/2-cusps and generic inflection points are given.